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Wish you were here: Meetings, no meetings, meeting reports [Editorial]

We've all been saying it: These are unprecedented times. The impacts of the COVID-19 pandemic are incredibly wide-ranging and affect all facets of life. One that is hitting the scientific community very hard is the cancellation of meetings, large and small. While we are well-versed in connecting with colleagues and collaborators across a variety of online platforms, these do not replace the immensely gratifying aspects of attending meetings in person: the pleasure of catching up with old friends and making new ones, the insights gained from having real-time conversations with others working on the same topic but with different expertise and perspectives, and the stimulating new scientific ideas we carry home. We have all been feeling the disappointment as we learn that one meeting after another is forced to cancel, from the vibrant ASBMB annual meeting to summer conferences of all types.Another loss from the appropriate but painful decision to cancel the ASBMB annual meeting was the chance to hear from our Herbert Tabor Early Career Investigator Awardees, who represent the best science published in JBC in the preceding year. This year, the competition was particularly fierce. We hope and anticipate that we will be able to hear from the winners at next year's ASBMB annual meeting. But in the meantime, we want to raise a toast to Wenchao Zhao, Yue Yang, Manisha Dagar, Febin Varghese, and Ayumi Nagashima-Kasahara as our 2020 winners. We've captured their award-winning 2019 papers (1–5) on the JBC website (6), and extended profiles of the...




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Correction: Mitochondrial and nuclear genomic responses to loss of LRPPRC expression. [Additions and Corrections]

VOLUME 285 (2010) PAGES 13742–13747In Fig. 1E, passage 10, the splicing of a non-adjacent lane from the same immunoblot was not marked. This error has now been corrected and does not affect the results or conclusions of this work.jbc;295/16/5533/F1F1F1Figure 1E.




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Three distinct glycosylation pathways are involved in the decoration of Lactococcus lactis cell wall glycopolymers [Microbiology]

Extracytoplasmic sugar decoration of glycopolymer components of the bacterial cell wall contributes to their structural diversity. Typically, the molecular mechanism that underpins such a decoration process involves a three-component glycosylation system (TGS) represented by an undecaprenyl-phosphate (Und-P) sugar-activating glycosyltransferase (Und-P GT), a flippase, and a polytopic glycosyltransferase (PolM GT) dedicated to attaching sugar residues to a specific glycopolymer. Here, using bioinformatic analyses, CRISPR-assisted recombineering, structural analysis of cell wall–associated polysaccharides (CWPS) through MALDI-TOF MS and methylation analysis, we report on three such systems in the bacterium Lactococcus lactis. On the basis of sequence similarities, we first identified three gene pairs, csdAB, csdCD, and csdEF, each encoding an Und-P GT and a PolM GT, as potential TGS component candidates. Our experimental results show that csdAB and csdCD are involved in Glc side-chain addition on the CWPS components rhamnan and polysaccharide pellicle (PSP), respectively, whereas csdEF plays a role in galactosylation of lipoteichoic acid (LTA). We also identified a potential flippase encoded in the L. lactis genome (llnz_02975, cflA) and confirmed that it participates in the glycosylation of the three cell wall glycopolymers rhamnan, PSP, and LTA, thus indicating that its function is shared by the three TGSs. Finally, we observed that glucosylation of both rhamnan and PSP can increase resistance to bacteriophage predation and that LTA galactosylation alters L. lactis resistance to bacteriocin.




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Inhibition of the erythropoietin-producing receptor EPHB4 antagonizes androgen receptor overexpression and reduces enzalutamide resistance [Molecular Bases of Disease]

Prostate cancer (PCa) cells heavily rely on an active androgen receptor (AR) pathway for their survival. Enzalutamide (MDV3100) is a second-generation antiandrogenic drug that was approved by the Food and Drug Administration in 2012 to treat patients with castration-resistant prostate cancer (CRPC). However, emergence of resistance against this drug is inevitable, and it has been a major challenge to develop interventions that help manage enzalutamide-resistant CRPC. Erythropoietin-producing human hepatocellular (Eph) receptors are targeted by ephrin protein ligands and have a broad range of functions. Increasing evidence indicates that this signaling pathway plays an important role in tumorigenesis. Overexpression of EPH receptor B4 (EPHB4) has been observed in multiple types of cancer, being closely associated with proliferation, invasion, and metastasis of tumors. Here, using RNA-Seq analyses of clinical and preclinical samples, along with several biochemical and molecular methods, we report that enzalutamide-resistant PCa requires an active EPHB4 pathway that supports drug resistance of this tumor type. Using a small kinase inhibitor and RNAi-based gene silencing to disrupt EPHB4 activity, we found that these disruptions re-sensitize enzalutamide-resistant PCa to the drug both in vitro and in vivo. Mechanistically, we found that EPHB4 stimulates the AR by inducing proto-oncogene c-Myc (c-Myc) expression. Taken together, these results provide critical insight into the mechanism of enzalutamide resistance in PCa, potentially offering a therapeutic avenue for enhancing the efficacy of enzalutamide to better manage this common malignancy.




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Substrate recognition and ATPase activity of the E. coli cysteine/cystine ABC transporter YecSC-FliY [Microbiology]

Sulfur is essential for biological processes such as amino acid biogenesis, iron–sulfur cluster formation, and redox homeostasis. To acquire sulfur-containing compounds from the environment, bacteria have evolved high-affinity uptake systems, predominant among which is the ABC transporter family. Theses membrane-embedded enzymes use the energy of ATP hydrolysis for transmembrane transport of a wide range of biomolecules against concentration gradients. Three distinct bacterial ABC import systems of sulfur-containing compounds have been identified, but the molecular details of their transport mechanism remain poorly characterized. Here we provide results from a biochemical analysis of the purified Escherichia coli YecSC-FliY cysteine/cystine import system. We found that the substrate-binding protein FliY binds l-cystine, l-cysteine, and d-cysteine with micromolar affinities. However, binding of the l- and d-enantiomers induced different conformational changes of FliY, where the l- enantiomer–substrate-binding protein complex interacted more efficiently with the YecSC transporter. YecSC had low basal ATPase activity that was moderately stimulated by apo FliY, more strongly by d-cysteine–bound FliY, and maximally by l-cysteine– or l-cystine–bound FliY. However, at high FliY concentrations, YecSC reached maximal ATPase rates independent of the presence or nature of the substrate. These results suggest that FliY exists in a conformational equilibrium between an open, unliganded form that does not bind to the YecSC transporter and closed, unliganded and closed, liganded forms that bind this transporter with variable affinities but equally stimulate its ATPase activity. These findings differ from previous observations for similar ABC transporters, highlighting the extent of mechanistic diversity in this large protein family.




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Dopamine transporter trafficking and Rit2 GTPase: Mechanism of action and in vivo impact [Neurobiology]

Following its evoked release, dopamine (DA) signaling is rapidly terminated by presynaptic reuptake, mediated by the cocaine-sensitive DA transporter (DAT). DAT surface availability is dynamically regulated by endocytic trafficking, and direct protein kinase C (PKC) activation acutely diminishes DAT surface expression by accelerating DAT internalization. Previous cell line studies demonstrated that PKC-stimulated DAT endocytosis requires both Ack1 inactivation, which releases a DAT-specific endocytic brake, and the neuronal GTPase, Rit2, which binds DAT. However, it is unknown whether Rit2 is required for PKC-stimulated DAT endocytosis in DAergic terminals or whether there are region- and/or sex-dependent differences in PKC-stimulated DAT trafficking. Moreover, the mechanisms by which Rit2 controls PKC-stimulated DAT endocytosis are unknown. Here, we directly examined these important questions. Ex vivo studies revealed that PKC activation acutely decreased DAT surface expression selectively in ventral, but not dorsal, striatum. AAV-mediated, conditional Rit2 knockdown in DAergic neurons impacted baseline DAT surface:intracellular distribution in DAergic terminals from female ventral, but not dorsal, striatum. Further, Rit2 was required for PKC-stimulated DAT internalization in both male and female ventral striatum. FRET and surface pulldown studies in cell lines revealed that PKC activation drives DAT-Rit2 surface dissociation and that the DAT N terminus is required for both PKC-mediated DAT-Rit2 dissociation and DAT internalization. Finally, we found that Rit2 and Ack1 independently converge on DAT to facilitate PKC-stimulated DAT endocytosis. Together, our data provide greater insight into mechanisms that mediate PKC-regulated DAT internalization and reveal unexpected region-specific differences in PKC-stimulated DAT trafficking in bona fide DAergic terminals.




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ABC transporters control ATP release through cholesterol-dependent volume-regulated anion channel activity [Signal Transduction]

Purinergic signaling by extracellular ATP regulates a variety of cellular events and is implicated in both normal physiology and pathophysiology. Several molecules have been associated with the release of ATP and other small molecules, but their precise contributions have been difficult to assess because of their complexity and heterogeneity. Here, we report on the results of a gain-of-function screen for modulators of hypotonicity-induced ATP release using HEK-293 cells and murine cerebellar granule neurons, along with bioluminescence, calcium FLIPR, and short hairpin RNA–based gene-silencing assays. This screen utilized the most extensive genome-wide ORF collection to date, covering 90% of human, nonredundant, protein-encoding genes. We identified two ABCG1 (ABC subfamily G member 1) variants, which regulate cellular cholesterol, as modulators of hypotonicity-induced ATP release. We found that cholesterol levels control volume-regulated anion channel–dependent ATP release. These findings reveal novel mechanisms for the regulation of ATP release and volume-regulated anion channel activity and provide critical links among cellular status, cholesterol, and purinergic signaling.




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Correction: A dual druggable genome-wide siRNA and compound library screening approach identifies modulators of parkin recruitment to mitochondria. [Additions and Corrections]

VOLUME 295 (2020) PAGES 3285–3300An incorrect graph was used in Fig. 5C. This error has now been corrected. Additionally, some of the statistics reported in the legend and text referring to Fig. 5C were incorrect. The F statistics for Fig. 5C should state Fken(3,16) = 7.454, p < 0.01; FCCCP(1,16) = 102.9, p < 0.0001; Finteraction(3,16) = 7.480, p < 0.01. This correction does not affect the results or conclusions of this work.jbc;295/17/5835/F5F1F5Figure 5C.




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Deletion of fatty acid transport protein 2 (FATP2) in the mouse liver changes the metabolic landscape by increasing the expression of PPAR{alpha}-regulated genes [Lipids]

Fatty acid transport protein 2 (FATP2) is highly expressed in the liver, small intestine, and kidney, where it functions in both the transport of exogenous long-chain fatty acids and the activation of very-long-chain fatty acids. Here, using a murine model, we investigated the phenotypic impacts of deleting FATP2, followed by a transcriptomic analysis using unbiased RNA-Seq to identify concomitant changes in the liver transcriptome. WT and FATP2-null (Fatp2−/−) mice (5 weeks) were maintained on a standard chow diet for 6 weeks. The Fatp2−/− mice had reduced weight gain, lowered serum triglyceride, and increased serum cholesterol levels and attenuated dietary fatty acid absorption. Transcriptomic analysis of the liver revealed 258 differentially expressed genes in male Fatp2−/− mice and a total of 91 in female Fatp2−/− mice. These genes mapped to the following gene ontology categories: fatty acid degradation, peroxisome biogenesis, fatty acid synthesis, and retinol and arachidonic acid metabolism. Targeted RT-quantitative PCR verified the altered expression of selected genes. Of note, most of the genes with increased expression were known to be regulated by peroxisome proliferator–activated receptor α (PPARα), suggesting that FATP2 activity is linked to a PPARα-specific proximal ligand. Targeted metabolomic experiments in the Fatp2−/− liver revealed increases of total C16:0, C16:1, and C18:1 fatty acids; increases in lipoxin A4 and prostaglandin J2; and a decrease in 20-hydroxyeicosatetraenoic acid. We conclude that the expression of FATP2 in the liver broadly affects the metabolic landscape through PPARα, indicating that FATP2 provides an important role in liver lipid metabolism through its transport or activation activities.




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Detailed analyses of the crucial functions of Zn transporter proteins in alkaline phosphatase activation [Enzymology]

Numerous zinc ectoenzymes are metalated by zinc and activated in the compartments of the early secretory pathway before reaching their destination. Zn transporter (ZNT) proteins located in these compartments are essential for ectoenzyme activation. We have previously reported that ZNT proteins, specifically ZNT5–ZNT6 heterodimers and ZNT7 homodimers, play critical roles in the activation of zinc ectoenzymes, such as alkaline phosphatases (ALPs), by mobilizing cytosolic zinc into these compartments. However, this process remains incompletely understood. Here, using genetically-engineered chicken DT40 cells, we first determined that Zrt/Irt-like protein (ZIP) transporters that are localized to the compartments of the early secretory pathway play only a minor role in the ALP activation process. These transporters included ZIP7, ZIP9, and ZIP13, performing pivotal functions in maintaining cellular homeostasis by effluxing zinc out of the compartments. Next, using purified ALP proteins, we showed that zinc metalation on ALP produced in DT40 cells lacking ZNT5–ZNT6 heterodimers and ZNT7 homodimers is impaired. Finally, by genetically disrupting both ZNT5 and ZNT7 in human HAP1 cells, we directly demonstrated that the tissue-nonspecific ALP-activating functions of both ZNT complexes are conserved in human cells. Furthermore, using mutant HAP1 cells, we uncovered a previously-unrecognized and unique spatial regulation of ZNT5–ZNT6 heterodimer formation, wherein ZNT5 recruits ZNT6 to the Golgi apparatus to form the heterodimeric complex. These findings fill in major gaps in our understanding of the molecular mechanisms underlying zinc ectoenzyme activation in the compartments of the early secretory pathway.




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Processivity of dextransucrases synthesizing very-high-molar-mass dextran is mediated by sugar-binding pockets in domain V [Glycobiology and Extracellular Matrices]

The dextransucrase DSR-OK from the Gram-positive bacterium Oenococcus kitaharae DSM17330 produces a dextran of the highest molar mass reported to date (∼109 g/mol). In this study, we selected a recombinant form, DSR-OKΔ1, to identify molecular determinants involved in the sugar polymerization mechanism and that confer its ability to produce a very-high-molar-mass polymer. In domain V of DSR-OK, we identified seven putative sugar-binding pockets characteristic of glycoside hydrolase 70 (GH70) glucansucrases that are known to be involved in glucan binding. We investigated their role in polymer synthesis through several approaches, including monitoring of dextran synthesis, affinity assays, sugar binding pocket deletions, site-directed mutagenesis, and construction of chimeric enzymes. Substitution of only two stacking aromatic residues in two consecutive sugar-binding pockets (variant DSR-OKΔ1-Y1162A-F1228A) induced quasi-complete loss of very-high-molar-mass dextran synthesis, resulting in production of only 10–13 kg/mol polymers. Moreover, the double mutation completely switched the semiprocessive mode of DSR-OKΔ1 toward a distributive one, highlighting the strong influence of these pockets on enzyme processivity. Finally, the position of each pocket relative to the active site also appeared to be important for polymer elongation. We propose that sugar-binding pockets spatially closer to the catalytic domain play a major role in the control of processivity. A deep structural characterization, if possible with large-molar-mass sugar ligands, would allow confirming this hypothesis.




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The mitochondrial protein PGAM5 suppresses energy consumption in brown adipocytes by repressing expression of uncoupling protein 1 [Metabolism]

Accumulating evidence suggests that brown adipose tissue (BAT) is a potential therapeutic target for managing obesity and related diseases. PGAM family member 5, mitochondrial serine/threonine protein phosphatase (PGAM5), is a protein phosphatase that resides in the mitochondria and regulates many biological processes, including cell death, mitophagy, and immune responses. Because BAT is a mitochondria-rich tissue, we have hypothesized that PGAM5 has a physiological function in BAT. We previously reported that PGAM5-knockout (KO) mice are resistant to severe metabolic stress. Importantly, lipid accumulation is suppressed in PGAM5-KO BAT, even under unstressed conditions, raising the possibility that PGAM5 deficiency stimulates lipid consumption. However, the mechanism underlying this observation is undetermined. Here, using an array of biochemical approaches, including quantitative RT-PCR, immunoblotting, and oxygen consumption assays, we show that PGAM5 negatively regulates energy expenditure in brown adipocytes. We found that PGAM5-KO brown adipocytes have an enhanced oxygen consumption rate and increased expression of uncoupling protein 1 (UCP1), a protein that increases energy consumption in the mitochondria. Mechanistically, we found that PGAM5 phosphatase activity and intramembrane cleavage are required for suppression of UCP1 activity. Furthermore, utilizing a genome-wide siRNA screen in HeLa cells to search for regulators of PGAM5 cleavage, we identified a set of candidate genes, including phosphatidylserine decarboxylase (PISD), which catalyzes the formation of phosphatidylethanolamine at the mitochondrial membrane. Taken together, these results indicate that PGAM5 suppresses mitochondrial energy expenditure by down-regulating UCP1 expression in brown adipocytes and that its phosphatase activity and intramembrane cleavage are required for UCP1 suppression.




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NF-{kappa}B mediates lipopolysaccharide-induced alternative pre-mRNA splicing of MyD88 in mouse macrophages [Signal Transduction]

Although a robust inflammatory response is needed to combat infection, this response must ultimately be terminated to prevent chronic inflammation. One mechanism that terminates inflammatory signaling is the production of alternative mRNA splice forms in the Toll-like receptor (TLR) signaling pathway. Whereas most genes in the TLR pathway encode positive mediators of inflammatory signaling, several, including that encoding the MyD88 signaling adaptor, also produce alternative spliced mRNA isoforms that encode dominant-negative inhibitors of the response. Production of these negatively acting alternatively spliced isoforms is induced by stimulation with the TLR4 agonist lipopolysaccharide (LPS); thus, this alternative pre-mRNA splicing represents a negative feedback loop that terminates TLR signaling and prevents chronic inflammation. In the current study, we investigated the mechanisms regulating the LPS-induced alternative pre-mRNA splicing of the MyD88 transcript in murine macrophages. We found that 1) the induction of the alternatively spliced MyD88 form is due to alternative pre-mRNA splicing and not caused by another RNA regulatory mechanism, 2) MyD88 splicing is regulated by both the MyD88- and TRIF-dependent arms of the TLR signaling pathway, 3) MyD88 splicing is regulated by the NF-κB transcription factor, and 4) NF-κB likely regulates MyD88 alternative pre-mRNA splicing per se rather than regulating splicing indirectly by altering MyD88 transcription. We conclude that alternative splicing of MyD88 may provide a sensitive mechanism that ensures robust termination of inflammation for tissue repair and restoration of normal tissue homeostasis once an infection is controlled.




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Biophysical characterization of SARAH domain-mediated multimerization of Hippo pathway complexes in Drosophila [Signal Transduction]

Hippo pathway signaling limits cell growth and proliferation and maintains the stem-cell niche. These cellular events result from the coordinated activity of a core kinase cassette that is regulated, in part, by interactions involving Hippo, Salvador, and dRassF. These interactions are mediated by a conserved coiled-coil domain, termed SARAH, in each of these proteins. SARAH domain–mediated homodimerization of Hippo kinase leads to autophosphorylation and activation. Paradoxically, SARAH domain–mediated heterodimerization between Hippo and Salvador enhances Hippo kinase activity in cells, whereas complex formation with dRassF inhibits it. To better understand the mechanism by which each complex distinctly modulates Hippo kinase and pathway activity, here we biophysically characterized the entire suite of SARAH domain–mediated complexes. We purified the three SARAH domains from Drosophila melanogaster and performed an unbiased pulldown assay to identify all possible interactions, revealing that isolated SARAH domains are sufficient to recapitulate the cellular assemblies and that Hippo is a universal binding partner. Additionally, we found that the Salvador SARAH domain homodimerizes and demonstrate that this interaction is conserved in Salvador's mammalian homolog. Using native MS, we show that each of these complexes is dimeric in solution. We also measured the stability of each SARAH domain complex, finding that despite similarities at both the sequence and structural levels, SARAH domain complexes differ in stability. The identity, stoichiometry, and stability of these interactions characterized here comprehensively reveal the nature of SARAH domain–mediated complex formation and provide mechanistic insights into how SARAH domain–mediated interactions influence Hippo pathway activity.




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Mechanistic insights explain the transforming potential of the T507K substitution in the protein-tyrosine phosphatase SHP2 [Signal Transduction]

The protein-tyrosine phosphatase SHP2 is an allosteric enzyme critical for cellular events downstream of growth factor receptors. Mutations in the SHP2 gene have been linked to many different types of human diseases, including developmental disorders, leukemia, and solid tumors. Unlike most SHP2-activating mutations, the T507K substitution in SHP2 is unique in that it exhibits oncogenic Ras-like transforming activity. However, the biochemical basis of how the SHP2/T507K variant elicits transformation remains unclear. By combining kinetic and biophysical methods, X-ray crystallography, and molecular modeling, as well as using cell biology approaches, here we uncovered that the T507K substitution alters both SHP2 substrate specificity and its allosteric regulatory mechanism. We found that although SHP2/T507K exists in the closed, autoinhibited conformation similar to the WT enzyme, the interactions between its N-SH2 and protein-tyrosine phosphatase domains are weakened such that SHP2/T507K possesses a higher affinity for the scaffolding protein Grb2-associated binding protein 1 (Gab1). We also discovered that the T507K substitution alters the structure of the SHP2 active site, resulting in a change in SHP2 substrate preference for Sprouty1, a known negative regulator of Ras signaling and a potential tumor suppressor. Our results suggest that SHP2/T507K's shift in substrate specificity coupled with its preferential association of SHP2/T507K with Gab1 enable the mutant SHP2 to more efficiently dephosphorylate Sprouty1 at pTyr-53. This dephosphorylation hyperactivates Ras signaling, which is likely responsible for SHP2/T507K's Ras-like transforming activity.




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MtrP, a putative methyltransferase in Corynebacteria, is required for optimal membrane transport of trehalose mycolates [Lipids]

Pathogenic bacteria of the genera Mycobacterium and Corynebacterium cause severe human diseases such as tuberculosis (Mycobacterium tuberculosis) and diphtheria (Corynebacterium diphtheriae). The cells of these species are surrounded by protective cell walls rich in long-chain mycolic acids. These fatty acids are conjugated to the disaccharide trehalose on the cytoplasmic side of the bacterial cell membrane. They are then transported across the membrane to the periplasm where they act as donors for other reactions. We have previously shown that transient acetylation of the glycolipid trehalose monohydroxycorynomycolate (hTMCM) enables its efficient transport to the periplasm in Corynebacterium glutamicum and that acetylation is mediated by the membrane protein TmaT. Here, we show that a putative methyltransferase, encoded at the same genetic locus as TmaT, is also required for optimal hTMCM transport. Deletion of the C. glutamicum gene NCgl2764 (Rv0224c in M. tuberculosis) abolished acetyltrehalose monocorynomycolate (AcTMCM) synthesis, leading to accumulation of hTMCM in the inner membrane and delaying its conversion to trehalose dihydroxycorynomycolate (h2TDCM). Complementation with NCgl2764 normalized turnover of hTMCM to h2TDCM. In contrast, complementation with NCgl2764 derivatives mutated at residues essential for methyltransferase activity failed to rectify the defect, suggesting that NCgl2764/Rv0224c encodes a methyltransferase, designated here as MtrP. Comprehensive analyses of the individual mtrP and tmaT mutants and of a double mutant revealed strikingly similar changes across several lipid classes compared with WT bacteria. These findings indicate that both MtrP and TmaT have nonredundant roles in regulating AcTMCM synthesis, revealing additional complexity in the regulation of trehalose mycolate transport in the Corynebacterineae.




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Genetic evidence for reconfiguration of DNA polymerase {theta} active site for error-free translesion synthesis in human cells [DNA and Chromosomes]

The action mechanisms revealed by the biochemical and structural analyses of replicative and translesion synthesis (TLS) DNA polymerases (Pols) are retained in their cellular roles. In this regard, DNA polymerase θ differs from other Pols in that whereas purified Polθ misincorporates an A opposite 1,N6-ethenodeoxyadenosine (ϵdA) using an abasic-like mode, Polθ performs predominantly error-free TLS in human cells. To test the hypothesis that Polθ adopts a different mechanism for replicating through ϵdA in human cells than in the purified Pol, here we analyze the effects of mutations in the two highly conserved tyrosine residues, Tyr-2387 and Tyr-2391, in the Polθ active site. Our findings that these residues are indispensable for TLS by the purified Pol but are not required in human cells, as well as other findings, provide strong evidence that the Polθ active site is reconfigured in human cells to stabilize ϵdA in the syn conformation for Hoogsteen base pairing with the correct nucleotide. The evidence that a DNA polymerase can configure its active site entirely differently in human cells than in the purified Pol establishes a new paradigm for DNA polymerase function.




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5-Ethynyl-2'-deoxycytidine and 5-ethynyl-2'-deoxyuridine are differentially incorporated in cells infected with HSV-1, HCMV, and KSHV viruses [Microbiology]

Nucleoside analogues are a valuable experimental tool. Incorporation of these molecules into newly synthesized DNA (i.e. pulse-labeling) is used to monitor cell proliferation or to isolate nascent DNA. Some of the most common nucleoside analogues used for pulse-labeling of DNA in cells are the deoxypyrimidine analogues 5-ethynyl-2'-deoxyuridine (EdU) and 5-ethynyl-2'-deoxycytidine (EdC). Click chemistry enables conjugation of an azide molecule tagged with a fluorescent dye or biotin to the alkyne of the analog, which can then be used to detect incorporation of EdU and EdC into DNA. The use of EdC is often recommended because of the potential cytotoxicity associated with EdU during longer incubations. Here, by comparing the relative incorporation efficiencies of EdU and EdC during short 30-min pulses, we demonstrate significantly lower incorporation of EdC than of EdU in noninfected human fibroblast cells or in cells infected with either human cytomegalovirus or Kaposi's sarcoma-associated herpesvirus. Interestingly, cells infected with herpes simplex virus type-1 (HSV-1) incorporated EdC and EdU at similar levels during short pulses. Of note, exogenous expression of HSV-1 thymidine kinase increased the incorporation efficiency of EdC. These results highlight the limitations when using substituted pyrimidine analogues in pulse-labeling and suggest that EdU is the preferable nucleoside analogue for short pulse-labeling experiments, resulting in increased recovery and sensitivity for downstream applications. This is an important discovery that may help to better characterize the biochemical properties of different nucleoside analogues with a given kinase, ultimately leading to significant differences in labeling efficiency of nascent DNA.




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EDB to enhance support for students with autism spectrum disorders




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Profiles of kindergartens posted online




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Revamp of Committee on Self-financing Post-secondary Education announced




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New round of applications under Quality Enhancement Support Scheme opens




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HKEAA submits 2019 Territory-wide System Assessment Report




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Speech by SED at opening ceremony of Learning and Teaching Expo 2019




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Appointments to Vocational Training Council




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Appointments to Education Commission announced




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Appointment of Chairman of Council of Lingnan University




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EDB's response to Ombudsman's direct investigation report




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Appointments to Quality Education Fund Steering Committee




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Task Force on Promotion of Vocational and Professional Education and Training submits review report to EDB




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Temporary closure of EDB public facilities from tomorrow




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EDB progressively disburses anti-epidemic subsidies and support grants to schools




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Integration and Application of Knowledge, Experience and Resources Supporting Students with Special Educational Needs in the Epidemic




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Appointment of new member to Advisory Committee on Gifted Education




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Loan repayment by self-financing post-secondary institutions under Start-up Loan Scheme, non-profit-making international schools and student loan repayers to be deferred for two years




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Re-appointment of Chairman of Council of Education University of Hong Kong




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Primary One Central Allocation results to be posted to parents in early June




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Physio support in COVID-19 recovery

(Flinders University) New physiotherapy guidelines are targeting COVID-19 patient recovery for respiratory management, exercise and mobilisation in acute hospital wards and Intensive Care Units. The new guidelines published in Australian Journal of Physiotherapy aim to prevent complications of the respiratory system and muscle deconditioning, speed up recovery from mechanical ventilation, and improve long-term physical function and recovery.




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LSU Health study suggests nicotine exposure alone leads to pulmonary hypertension

(Louisiana State University Health Sciences Center) A study conducted at LSU Health New Orleans has shown for the first time that chronic exposure to inhaled nicotine alone increases blood pressure in both the body's general circulation and in the lungs that can lead to pulmonary hypertension. The study also found that nicotine-induced pulmonary hypertension is accompanied by changes in the size, shape and function (remodeling) of the blood vessels in the lung and the right lower chamber of the heart.




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Could a polio vaccine stop the coronavirus pandemic? (video)

(American Chemical Society) The COVID-19 pandemic has scientists considering a few less-conventional options while vaccines against SARS-CoV-2 are being developed. One option might be the oral polio vaccine. We chatted with one of the researchers proposing the idea -- Robert Gallo, M.D. -- to understand why a vaccine that hasn't been used in the U.S. for two decades might provide short-term protection against this new coronavirus: https://youtu.be/Wqw4aX4c33c.




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Ultraviolet light exposes contagion spread from improper PPE use

(Florida Atlantic University) Despite PPE use, reports show that many health care workers contracted COVID-19. A novel training technique reinforces the importance of using proper procedures to put on and take off PPE when caring for patients during the pandemic. Researchers vividly demonstrate how aerosol-generating procedures can lead to exposure of the contagion with improper PPE use. The most common error made by the health care workers was contaminating the face or forearms during PPE removal.




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Dog tests positive for COVID-19

The Agriculture, Fisheries & Conservation Department (AFCD) today said a pet dog has tested positive for the COVID-19 virus. 

The case involves a German Shepherd dog whose owners live in Pok Fu Lam. This follows an earlier case in which a 17-year-old Pomeranian dog tested weak positive during repeated tests for the virus.

  

When the German Shepherd's owner was confirmed with COVID-19, it was sent for quarantine with another mixed breed dog from the same residence to the animal keeping facility at the Hong Kong-Zhuhai-Macao Bridge's Hong Kong Port yesterday.

 

No positive results were obtained from the mixed breed dog and neither dog has shown any signs of the disease.

 

The department will continue to closely monitor both dogs and conduct repeated tests on them.

 

It strongly advises that mammalian pet animals including dogs and cats from households with people confirmed as infected with COVID-19, or close contacts of COVID-19 infected people, should be put under quarantine in AFCD facilities.

 

The department emphasised that there is currently no evidence pet animals can be a source of COVID-19 for humans or that this virus can cause the disease in dogs.

 

Pet owners are reminded to maintain good hygiene practices and under no circumstances should they abandon their pets.




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Support schemes applications open

The Government today announced that applications are open for several support schemes following the funding approval of the second round of the Anti-epidemic Fund and other relief measures by the Legislative Council Finance Committee.

 

The Club-house Subsidy Scheme, which provides a one-off subsidy of $100,000 to eligible club-houses, is now open for application. The deadline for application is May 18.

 

Upon submission of the completed application form and supporting documents, the disbursement of subsidies could generally be made in around two weeks.

 

The Travel Agents & Practitioners Support Scheme and the Hotel Sector Support Scheme are also open for applications, with the deadlines on June 15 and May 18 respectively.

 

The Subsidy Scheme for the Refuse Transfer Station Account Holders for Transporting Municipal Solid Waste, which offers a one-off subsidy of $8,000 to each of the eligible private municipal solid waste collectors operating in the first quarter, was also endorsed.

 

To ease the application procedures, the Environmental Protection Department will post cheques to recipients of this special subsidy in about a week after the funding endorsement.

 

Meanwhile, the total guarantee commitment of the Special 100% Loan Guarantee under the SME Financing Guarantee Scheme has been increased to $50 billion.

 

The maximum loan amount per enterprise has been increased to $4 million and the principal moratorium arrangement has been extended to the first 12 months.

 

The Special 100% Loan Guarantee will start receiving applications from April 20 and the application period has been extended to one year.




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About the cover: The Fine–Petrović Polygons and the Newton–Puiseux Method for Algebraic Ordinary Differential Equations

Vladimir Dragović and Irina Goryuchkina
Bull. Amer. Math. Soc. 57 (2020), 293-299.
Abstract, references and article information




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HK airport’s fresh approach

In March, Hong Kong International Airport (HKIA) became the first in the world to be certified as an International Air Transport Association (IATA) Center of Excellence for Perishable Logistics (CEIV Fresh) Partner Airport.

 

Two of the airport’s cargo terminal operators, Hong Kong Air Cargo Terminals Limited (HACTL) and Cathay Pacific Services Limited (CPSL) have achieved IATA CEIV Fresh Certification, while Cathay Pacific recently became the world’s first airline to be certified.

 

IATA created the Centre of Excellence for Independent Validators (CEIV) to help organisations involved in the air cargo supply chain achieve handling excellence.

 

The certification underscores the speed, consistency and efficiency of all HKIA stakeholders when it comes to the treatment and transportation of perishable products.

 

It also helps to ensure food safety, and reduce food wastage and loss along the supply chain.

 

Quality benchmark

Hong Kong Air Cargo Terminals Limited Chief Executive Wilson Kwong said the main value of the accreditation is that it provides a universally recognised standard.

 

“It gives assurance to the various stakeholders that we have, and we are adhering to the highest possible standards.”

 

Both accredited cargo terminal operators HACTL and CPSL have set up perishable cargo handling areas with truck docks next to the apron.

 

As soon as the perishable goods are unloaded from the aircraft, they are immediately transported to the handling area.

 

The clearance and sampling checks have been streamlined to minimise the time taken to unload the goods. There are cold rooms set at tailored temperatures for various kinds of perishable cargo.

 

Their staff training and handling process have also been assessed and certified for their compliance with the global industry standards.

 

Cathay Pacific Services Limited Chief Executive Officer Jenny Lam noted that one of the challenges in meeting the certification standard is training its 2,000 employees in handling and storing perishable goods.

 

“They first have to identify what types of perishables they are, such as are they flowers, are they fruits, are they meat, so that they know how to segregate the storage.

 

“Secondly, they gain knowledge about certain fruits that cannot be put close to each other such as bananas and apples.”

 

Growth opportunities

In 2018, the airport handled about 380,000 tonnes of perishable cargo - a rise of 12% on 2017, with perishables accounting for about 8% of total air cargo volume.

 

Airport Authority Commercial Executive Director Cissy Chan explained that temperature-controlled air freight is one of the fastest growing segments in the air cargo market.

 

She believes with the new certification, the airport is well-placed to capture the increasing growth opportunities in the market for fresh and perishable goods.

 

“With the opening of the Hong Kong-Zhuhai-Macao Bridge, the transport time between the airport and the Greater Bay Area, notably the western part of the Pearl River Delta, will be further cut down.

 

“So this will put us in an even better position to become the transhipment hub for these perishables for the entire bay area.”

 

Extra backing

To support the growing demand for perishables, the Airport Authority has provided additional cool dollies, so there are now more than 30 for use by the whole airport community. It is also building apron shelters to protect the perishables from ambient weather elements.

 

Cathay Pacific Cargo Service Delivery General Manager Frosti Lau said they would work closely with the authority and its cargo terminal to see what new investments are required to handle the increasing demand.




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HK Airport sets green standard

The Airport Authority expanded the scope of its food waste recycling programme in 2011 to cover Hong Kong International Airport business partners, including restaurants and lounges operating in terminal buildings, as well as airline catering companies, hotels and cargo terminals.

 

In 2017-18, over 2,000 tonnes of food waste from 17 airport business partners were collected for recycling.

 

Rainie Ho, the supervisor of one participating restaurant, said staff make every effort to collect food waste on a constant basis.

 

“We have three bins of recycled food waste, including eggs, toast, bread, chicken, meat, pork bones, tea and coffee every day.”

 

Ms Ho gave kudos to the Airport Authority for making the process simple.

 

“The Airport Authority provides us with garbage bags every month. We explain to our staff that the red bags are for food waste, while the black ones are for general rubbish. This makes it easier for them to remember and handle.”

 

Airport Authority Assistant General Manager (Sustainability) Mike Kilburn is the facilitator of the food waste recycling programme. He hoped to encourage more business partners to join by making the scheme as trouble-free as possible.

 

“This is an example of an easy, useful and free programme because the contractor comes to collect from each company and the contractor provides a clean rubbish bin for the food waste, they take the food waste away, they wash the bin and then they bring it back clean.

 

“And it is useful because the food waste is not just sent to the landfill, but it is turned into fish meal so it goes back into the food chain because the fish meal is fed to the fish and the people can eat the fish, so it is a very complete system.”

 

Surplus food collection

In addition to food waste recycling, the authority promotes the Food Rescue Programme in co-operation with a local non-governmental organisation called Food Angel.

 

In 2013, the authority helped Food Angel to purchase a refrigerated truck and covered the cost of collecting surplus food from business partners on the airport island.

 

By 2014, a central storage room was set up in the terminal building to collect even more surplus food from catering outlets.

 

By proving it can reduce its environmental impact by working closely with the entire airport community, the authority was recognised at the 2018 Hong Kong Awards for Environmental Excellence where it won the Gold Award for the Public & Community Services Sector.

 

Future prep

In 2018, the authority launched a voluntary municipal solid waste charging pilot scheme to achieve waste reduction.

 

It has assisted more than 200 tenants with measuring their waste generation and calculating what it would cost to dump it in the future.

 

Another participating restaurant manager Alfred Lau explained that the pilot scheme helps restaurants gear up for the polluter-pays principle.

 

“A mock monthly invoice was issued to us, showing the quantity of waste disposed and the estimated disposal charge. Now we understand that by reducing our waste, we will pay less in the end.”

 

Mr Lau believes the pilot scheme encourages eateries to alter their disposal behaviour by recycling as much food waste as possible.

 

“Our disposed waste amount fell sharply once we learnt useful ways to recycle. Our restaurant is located in the restricted area of the airport where drinks are not allowed to be brought inside. So many passengers buy bottled drinks and create a large amount of plastic waste. Just by recycling plastic bottles, our waste decreased significantly.”

 

The authority said it is proud to be the driving force behind waste reduction.

 

“We make it easy for them because we do all the organisation, we make it useful because they can help them to prepare, and it is free for them to join the programme. This is very important for us because as the Airport Authority, our job is to create a concept that other people can follow and if you address those three criteria, you make it very hard for them to say no to you. We take away their reasons to say no, so it is easy for them to join our scheme,” said Mr Kilburn.

 

The Hong Kong Awards for Environmental Excellence is led by the Environmental Campaign Committee alongside the Environmental Protection Department and in conjunction with nine organisations. The objective is to reduce Hong Kong’s environmental impact by promoting environmental management.

 

The Airport Authority’s current target is to reduce, recycle and recover 50% of all its waste by 2021.




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