Heterotrimeric G-proteins are signaling switches broadly divided into four families based on the sequence and functional similarity of their Gα subunits: Gs, Gi/o, Gq/11, and G12/13. Artificial mutations that activate Gα subunits of each of these families have long been known to induce oncogenic transformation in experimental systems. With the advent of next-generation sequencing, activating hotspot mutations in Gs, Gi/o, or Gq/11 proteins have also been identified in patient tumor samples. In contrast, patient tumor-associated G12/13 mutations characterized to date lead to inactivation rather than activation. By using bioinformatic pathway analysis and signaling assays, here we identified cancer-associated hotspot mutations in Arg-200 of Gα13 (encoded by GNA13) as potent activators of oncogenic signaling. First, we found that components of a G12/13-dependent signaling cascade that culminates in activation of the Hippo pathway effectors YAP and TAZ is frequently altered in bladder cancer. Up-regulation of this signaling cascade correlates with increased YAP/TAZ activation transcriptional signatures in this cancer type. Among the G12/13 pathway alterations were mutations in Arg-200 of Gα13, which we validated to promote YAP/TAZ-dependent (TEAD) and MRTF-A/B-dependent (SRE.L) transcriptional activity. We further showed that this mechanism relies on the same RhoGEF-RhoGTPase cascade components that are up-regulated in bladder cancers. Moreover, Gα13 Arg-200 mutants induced oncogenic transformation in vitro as determined by focus formation assays. In summary, our findings on Gα13 mutants establish that naturally occurring hotspot mutations in Gα subunits of any of the four families of heterotrimeric G-proteins are putative cancer drivers.

The inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), which form tetrameric channels, play pivotal roles in regulating the spatiotemporal patterns of intracellular calcium signals. Mutations in IP3Rs have been increasingly associated with many debilitating human diseases such as ataxia, Gillespie syndrome, and generalized anhidrosis. However, how these mutations affect IP3R function, and how the perturbation of as-sociated calcium signals contribute to the pathogenesis and severity of these diseases remains largely uncharacterized. Moreover, many of these diseases occur as the result of autosomal dominant inheritance, suggesting that WT and mutant subunits associate in heterotetrameric channels. How the in-corporation of different numbers of mutant subunits within the tetrameric channels affects its activities and results in different disease phenotypes is also unclear. In this report, we investigated representative disease-associated missense mutations to determine their effects on IP3R channel activity. Additionally, we designed concatenated IP3R constructs to create tetrameric channels with a predefined subunit composition to explore the functionality of heteromeric channels. Using calcium imaging techniques to assess IP3R channel function, we observed that all the mutations studied resulted in severely attenuated Ca2+ release when expressed as homotetramers. However, some heterotetramers retained varied degrees of function dependent on the composition of the tetramer. Our findings suggest that the effect of mutations depends on the location of the mutation in the IP3R structure, as well as on the stoichiometry of mutant subunits assembled within the tetrameric channel. These studies provide insight into the pathogenesis and penetrance of these devastating human diseases.

IQGAP1 is a key scaffold protein that regulates numerous cellular processes and signaling pathways. Analogous to many other cellular proteins, IQGAP1 undergoes post-translational modifications, including phosphorylation. Nevertheless, very little is known about the specific sites of phosphorylation or the effects on IQGAP1 function. Here, using several approaches, including MS, site-directed mutagenesis, siRNA-mediated gene silencing, and chemical inhibitors, we identified the specific tyrosine residues that are phosphorylated on IQGAP1 and evaluated the effect on function. Tyr-172, Tyr-654, Tyr-855, and Tyr-1510 were phosphorylated on IQGAP1 when phosphotyrosine phosphatase activity was inhibited in cells. IQGAP1 was phosphorylated exclusively on Tyr-1510 under conditions with enhanced MET or c-Src signaling, including in human lung cancer cell lines. This phosphorylation was significantly reduced by chemical inhibitors of MET or c-Src or by siRNA-mediated knockdown of MET. To investigate the biological sequelae of phosphorylation, we generated a nonphosphorylatable IQGAP1 construct by replacing Tyr-1510 with alanine. The ability of hepatocyte growth factor, the ligand for MET, to promote AKT activation and cell migration was significantly greater when IQGAP1-null cells were reconstituted with IQGAP1 Y1510A than when cells were reconstituted with WT IQGAP1. Collectively, our data suggest that phosphorylation of Tyr-1510 of IQGAP1 alters cell function. Because increased MET signaling is implicated in the development and progression of several types of carcinoma, IQGAP1 may be a potential therapeutic target in selected malignancies.

Boris Macek
Feb 1, 2008; 7:299-307
Research

Ilka Wittig
Jul 1, 2007; 6:1215-1225
Research

Jonathan C. Trinidad
Aug 1, 2012; 11:215-229
Research

Qin Liu
Aug 1, 2007; 6:1299-1317
Research

Yi Zhang
Sep 1, 2005; 4:1240-1250
Research

Sean R. Collins
Mar 1, 2007; 6:439-450
Research

Roland Bruderer
May 1, 2015; 14:1400-1410
Research

Joris J. Benschop
Jul 1, 2007; 6:1198-1214
Research

Yu Xue
Sep 1, 2008; 7:1598-1608
Research

Claudio P. Albuquerque
Jul 1, 2008; 7:1389-1396
Research

Albrecht Gruhler
Mar 1, 2005; 4:310-327
Research

Martin R. Larsen
Jul 1, 2005; 4:873-886
Technology

Eiji Kinoshita
Apr 1, 2006; 5:749-757
Technology

Staphylococcus aureus adhesion to the host's skin and mucosae enables asymptomatic colonization and the establishment of infection. This process is facilitated by cell wall-anchored adhesins that bind to host ligands. Therapeutics targeting this process could provide significant clinical benefits; however, the development of anti-adhesives requires an in-depth knowledge of adhesion-associated factors and an assay amenable to high-throughput applications. Here, we describe the development of a sensitive and robust whole cell assay to enable the large-scale profiling of S. aureus adhesion to host ligands. To validate the assay, and to gain insight into cellular factors contributing to adhesion, we profiled a sequence-defined S. aureus transposon mutant library, identifying mutants with attenuated adhesion to human-derived fibronectin, keratin, and fibrinogen. Our screening approach was validated by the identification of known adhesion-related proteins, such as the housekeeping sortase responsible for covalently linking adhesins to the cell wall. In addition, we also identified genetic loci that could represent undescribed anti-adhesive targets. To compare and contrast the genetic requirements of adhesion to each host ligand, we generated a S. aureus Genetic Adhesion Network, which identified a core gene set involved in adhesion to all three host ligands, and unique genetic signatures. In summary, this assay will enable high-throughput chemical screens to identify anti-adhesives and our findings provide insight into the target space of such an approach.

Leukocidin ED (LukED) is a pore-forming toxin produced by Staphylococcus aureus, which lyses host cells and promotes virulence of the bacteria. LukED enables S. aureus to acquire iron by lysing erythrocytes, which depends on targeting the host receptor Duffy antigen receptor for chemokines (DARC). The toxin also targets DARC on the endothelium, contributing to the lethality observed during bloodstream infection in mice. LukED is comprised of two monomers: LukE and LukD. LukE binds to DARC and facilitates hemolysis, but the closely related Panton–Valentine leukocidin S (LukS-PV) does not bind to DARC and is not hemolytic. The interaction of LukE with DARC and the role this plays in hemolysis are incompletely characterized. To determine the domain(s) of LukE that are critical for DARC binding, we studied the hemolytic function of LukE–LukS-PV chimeras, in which areas of sequence divergence (divergence regions, or DRs) were swapped between the toxins. We found that two regions of LukE's rim domain contribute to hemolysis, namely residues 57–75 (DR1) and residues 182–196 (DR4). Interestingly, LukE DR1 is sufficient to render LukS-PV capable of DARC binding and hemolysis. Further, LukE, by binding DARC through DR1, promotes the recruitment of LukD to erythrocytes, likely by facilitating LukED oligomer formation. Finally, we show that LukE targets murine Darc through DR1 in vivo to cause host lethality. These findings expand our biochemical understanding of the LukE–DARC interaction and the role that this toxin-receptor pair plays in S. aureus pathophysiology.

Synapse loss is associated with motor and cognitive decline in multiple neurodegenerative disorders, and the cellular redistribution of tau is related to synaptic impairment in tauopathies, such as Alzheimer's disease and frontotemporal dementia. Here, we examined the cellular distribution of tau protein species in human tau overexpressing line 66 mice, a transgenic mouse model akin to genetic variants of frontotemporal dementia. Line 66 mice express intracellular tau aggregates in multiple brain regions and exhibit sensorimotor and motor learning deficiencies. Using a series of anti-tau antibodies, we observed, histologically, that nonphosphorylated transgenic human tau is enriched in synapses, whereas phosphorylated tau accumulates predominantly in cell bodies and axons. Subcellular fractionation confirmed that human tau is highly enriched in insoluble cytosolic and synaptosomal fractions, whereas endogenous mouse tau is virtually absent from synapses. Cytosolic tau was resistant to solubilization with urea and Triton X-100, indicating the formation of larger tau aggregates. By contrast, synaptic tau was partially soluble after Triton X-100 treatment and most likely represents aggregates of smaller size. MS corroborated that synaptosomal tau is nonphosphorylated. Tau enriched in the synapse of line 66 mice, therefore, appears to be in an oligomeric and nonphosphorylated state, and one that could have a direct impact on cognitive function.

Margrit Schwarz
Sep 1, 1998; 39:1833-1843
Articles

M el-Saadani
Apr 1, 1989; 30:627-630
Articles

Mohamad Navab
Jun 1, 2004; 45:993-1007
Thematic Reviews

JF Oram
Dec 1, 1996; 37:2473-2491
Reviews

JP Segrest
Feb 1, 1992; 33:141-166
Reviews

Saverio Cinti
Nov 1, 2005; 46:2347-2355
Research Articles

CJ Fielding
Feb 1, 1995; 36:211-228
Reviews

Facebook's power under scrutiny as Trump ban upheld Expert comment NCapeling 6 May 2021

Keeping Donald Trump’s Facebook ban in place shows the vast power social media platforms hold, raising questions of whether that power is appropriately used.

Kate Jones

From a human rights perspective, the Oversight Board’s decision is a strong one, and not at all surprising. The board decided Facebook was right to suspend the former president’s access to post content on Facebook and Instagram, but not indefinitely.

It found Donald Trump’s posts violated Facebook’s community standards because they amounted to praise or support of people engaged in violence and that, applying a human rights assessment, Facebook’s suspension of Trump was a necessary and proportionate restriction of his right to freedom of expression.

However the board also found Trump’s indefinite suspension was neither in conformity with a clear Facebook procedure nor consistent with its commitment to respect human rights. Its decision requires Facebook to make a new decision on the future of Donald Trump’s account, grounded in its rules.

While opinions on this result will differ, the increased call for clear and accessible rules and respect for human rights in their implementation that the Oversight Board brings to Facebook’s operations is welcome.

But the Oversight Board’s powers are limited to content moderation – Facebook declined to answer the board’s questions about amplification of Trump’s posts through the platform’s design decisions and algorithms. This limitation on the board’s role should be lifted. It is in content amplification, not just content moderation, that Facebook should face scrutiny and accountability for the sake of the human rights of its users.

Fundamentally, human rights is not a veneer which can mask or legitimize underlying power dynamics or public policy – those still fall to be assessed for themselves.

The Trump/Facebook saga does highlight the vast power Facebook and other major social media platforms have over political discussion and persuasion. Through granting or denying, or through amplifying or quietening the voices of political figures, Facebook has the power to shape politics, electorates, and democratic processes. Improving content moderation through the Oversight Board, although important, does little to constrain that power.

Facebook itself, unlike a government, has no accountability to the general public, and the Oversight Board must not distract us from the need for a full conversation about the extent to which Facebook’s power is appropriately held and properly wielded.

Emily Taylor

This decision marks a coming of age for Facebook’s content moderation process. For years, decisions to take down content or ban users have been opaque, conducted by a human workforce that Facebook and other platforms have been hesitant to acknowledge. The platforms have also been worried that being seen to exercise an editorial function might put at risk the legal protections which prevent the platforms being held responsible for user-generated content.

When the Oversight Board was first posited, observers questioned whether a body funded by Facebook could properly exercise a legitimate appeals function. Now there is a reasoned decision which partly supports the decision to de-platform a serving president, but also takes issue with the indefinite nature of the ban.

Facebook specifically asked the Oversight Board to consider specific challenges involved when the person involved is a political leader. The board concluded that Trump’s ‘status as head of state with a high position of trust not only imbued his words with greater force and credibility but also created risks that his followers would understand they could act with impunity’. The storming of the US Capitol and role President Trump played in stirring up the violence underlined that political leaders’ words can motivate others to take harmful actions.

Just as the events of January 6 remain shocking, it remains shocking that private platforms have exercised the power to curb the speech of a US president. It also remains shocking that the platforms sat back and took no action over the previous four years, but waited until the final days of the transition.

The board’s decision is an evolution in private-sector content moderation, with a diverse board giving a reasoned opinion on a Facebook decision. But to fully comply with the principles of open justice, board decisions should include more detail on the individuals who have made the decision – at present, it appears all members of the board review the decision but it is not clear which individuals were involved in its drafting, or that they were clear from conflicts. If the process is to gain respect as a truly independent oversight on the platform’s decisions, greater transparency over the identity of decision-makers will be needed.

Mark Zuckerberg expressed concern about Facebook becoming an arbiter of truth or free speech and, overall, the difficulty of having private companies managing the application of fundamental rights on their platforms has not been solved. Just because companies have the financial resources to do it, does not mean they necessarily should.

Yet no other international governance or arbitration system has emerged to handle the complexities of platform power over speech. In the context of that vacuum, the Oversight Board’s decision is a welcome step.

Hepatocyte nuclear factor-1β (HNF-1β) is a tissue-specific transcription factor that is required for normal kidney development and renal epithelial differentiation. Mutations of HNF-1β produce congenital kidney abnormalities and inherited renal tubulopathies. Here, we show that ablation of HNF-1β in mIMCD3 renal epithelial cells results in activation of β-catenin and increased expression of lymphoid enhancer–binding factor 1 (LEF1), a downstream effector in the canonical Wnt signaling pathway. Increased expression and nuclear localization of LEF1 are also observed in cystic kidneys from Hnf1b mutant mice. Expression of dominant-negative mutant HNF-1β in mIMCD3 cells produces hyperresponsiveness to exogenous Wnt ligands, which is inhibited by siRNA-mediated knockdown of Lef1. WT HNF-1β binds to two evolutionarily conserved sites located 94 and 30 kb from the mouse Lef1 promoter. Ablation of HNF-1β decreases H3K27 trimethylation repressive marks and increases β-catenin occupancy at a site 4 kb upstream to Lef1. Mechanistically, WT HNF-1β recruits the polycomb-repressive complex 2 that catalyzes H3K27 trimethylation. Deletion of the β-catenin–binding domain of LEF1 in HNF-1β–deficient cells abolishes the increase in Lef1 transcription and decreases the expression of downstream Wnt target genes. The canonical Wnt target gene, Axin2, is also a direct transcriptional target of HNF-1β through binding to negative regulatory elements in the gene promoter. These findings demonstrate that HNF-1β regulates canonical Wnt target genes through long-range effects on histone methylation at Wnt enhancers and reveal a new mode of active transcriptional repression by HNF-1β.

Expert

Phospholipase Cε (PLCε) is activated downstream of G protein–coupled receptors and receptor tyrosine kinases through direct interactions with small GTPases, including Rap1A and Ras. Although Ras has been reported to allosterically activate the lipase, it is not known whether Rap1A has the same ability or what its molecular mechanism might be. Rap1A activates PLCε in response to the stimulation of β-adrenergic receptors, translocating the complex to the perinuclear membrane. Because the C-terminal Ras association (RA2) domain of PLCε was proposed to the primary binding site for Rap1A, we first confirmed using purified proteins that the RA2 domain is indeed essential for activation by Rap1A. However, we also showed that the PLCε pleckstrin homology (PH) domain and first two EF hands (EF1/2) are required for Rap1A activation and identified hydrophobic residues on the surface of the RA2 domain that are also necessary. Small-angle X-ray scattering showed that Rap1A binding induces and stabilizes discrete conformational states in PLCε variants that can be activated by the GTPase. These data, together with the recent structure of a catalytically active fragment of PLCε, provide the first evidence that Rap1A, and by extension Ras, allosterically activate the lipase by promoting and stabilizing interactions between the RA2 domain and the PLCε core.

In animals, the response to chronic hypoxia is mediated by prolyl hydroxylases (PHDs) that regulate the levels of hypoxia-inducible transcription factor α (HIFα). PHD homologues exist in other types of eukaryotes and prokaryotes where they act on non HIF substrates. To gain insight into the factors underlying different PHD substrates and properties, we carried out biochemical and biophysical studies on PHD homologues from the cellular slime mold, Dictyostelium discoideum, and the protozoan parasite, Toxoplasma gondii, both lacking HIF. The respective prolyl-hydroxylases (DdPhyA and TgPhyA) catalyze prolyl-hydroxylation of S-phase kinase-associated protein 1 (Skp1), a reaction enabling adaptation to different dioxygen availability. Assays with full-length Skp1 substrates reveal substantial differences in the kinetic properties of DdPhyA and TgPhyA, both with respect to each other and compared with human PHD2; consistent with cellular studies, TgPhyA is more active at low dioxygen concentrations than DdPhyA. TgSkp1 is a DdPhyA substrate and DdSkp1 is a TgPhyA substrate. No cross-reactivity was detected between DdPhyA/TgPhyA substrates and human PHD2. The human Skp1 E147P variant is a DdPhyA and TgPhyA substrate, suggesting some retention of ancestral interactions. Crystallographic analysis of DdPhyA enables comparisons with homologues from humans, Trichoplax adhaerens, and prokaryotes, informing on differences in mobile elements involved in substrate binding and catalysis. In DdPhyA, two mobile loops that enclose substrates in the PHDs are conserved, but the C-terminal helix of the PHDs is strikingly absent. The combined results support the proposal that PHD homologues have evolved kinetic and structural features suited to their specific sensing roles.

DNA polymerases are today used throughout scientific research, biotechnology, and medicine, in part for their ability to interact with unnatural forms of DNA created by synthetic biologists. Here especially, natural DNA polymerases often do not have the “performance specifications” needed for transformative technologies. This creates a need for science-guided rational (or semi-rational) engineering to identify variants that replicate unnatural base pairs (UBPs), unnatural backbones, tags, or other evolutionarily novel features of unnatural DNA. In this review, we provide a brief overview of the chemistry and properties of replicative DNA polymerases and their evolved variants, focusing on the Klenow fragment of Taq DNA polymerase (Klentaq). We describe comparative structural, enzymatic, and molecular dynamics studies of WT and Klentaq variants, complexed with natural or noncanonical substrates. Combining these methods provides insight into how specific amino acid substitutions distant from the active site in a Klentaq DNA polymerase variant (ZP Klentaq) contribute to its ability to replicate UBPs with improved efficiency compared with Klentaq. This approach can therefore serve to guide any future rational engineering of replicative DNA polymerases.

Rhodopsin is a canonical class A photosensitive G protein–coupled receptor (GPCR), yet relatively few pharmaceutical agents targeting this visual receptor have been identified, in part due to the unique characteristics of its light-sensitive, covalently bound retinal ligands. Rhodopsin becomes activated when light isomerizes 11-cis-retinal into an agonist, all-trans-retinal (ATR), which enables the receptor to activate its G protein. We have previously demonstrated that, despite being covalently bound, ATR can display properties of equilibrium binding, yet how this is accomplished is unknown. Here, we describe a new approach for both identifying compounds that can activate and attenuate rhodopsin and testing the hypothesis that opsin binds retinal in equilibrium. Our method uses opsin-based fluorescent sensors, which directly report the formation of active receptor conformations by detecting the binding of G protein or arrestin fragments that have been fused onto the receptor's C terminus. We show that these biosensors can be used to monitor equilibrium binding of the agonist, ATR, as well as the noncovalent binding of β-ionone, an antagonist for G protein activation. Finally, we use these novel biosensors to observe ATR release from an activated, unlabeled receptor and its subsequent transfer to the sensor in real time. Taken together, these data support the retinal equilibrium binding hypothesis. The approach we describe should prove directly translatable to other GPCRs, providing a new tool for ligand discovery and mutant characterization.

Pyruvate kinase muscle isoform 2 (PKM2) is a key glycolytic enzyme and transcriptional coactivator and is critical for tumor metabolism. In cancer cells, native tetrameric PKM2 is phosphorylated or acetylated, which initiates a switch to a dimeric/monomeric form that translocates into the nucleus, causing oncogene transcription. However, it is not known how these post-translational modifications (PTMs) disrupt the oligomeric state of PKM2. We explored this question via crystallographic and biophysical analyses of PKM2 mutants containing residues that mimic phosphorylation and acetylation. We find that the PTMs elicit major structural reorganization of the fructose 1,6-bisphosphate (FBP), an allosteric activator, binding site, impacting the interaction with FBP and causing a disruption in oligomerization. To gain insight into how these modifications might cause unique outcomes in cancer cells, we examined the impact of increasing the intracellular pH (pHi) from ∼7.1 (in normal cells) to ∼7.5 (in cancer cells). Biochemical studies of WT PKM2 (wtPKM2) and the two mimetic variants demonstrated that the activity decreases as the pH is increased from 7.0 to 8.0, and wtPKM2 is optimally active and amenable to FBP-mediated allosteric regulation at pHi 7.5. However, the PTM mimetics exist as a mixture of tetramer and dimer, indicating that physiologically dimeric fraction is important and might be necessary for the modified PKM2 to translocate into the nucleus. Thus, our findings provide insight into how PTMs and pH regulate PKM2 and offer a broader understanding of its intricate allosteric regulation mechanism by phosphorylation or acetylation.

Defining discontinuous antigenic epitopes remains a substantial challenge, as exemplified by the case of lipid transfer polyproteins, which are common pollen allergens. Hydrogen/deuterium exchange monitored by NMR can be used to map epitopes onto folded protein surfaces, but only if the complex rapidly dissociates. Modifying the standard NMR-exchange measurement to detect substoichiometric complexes overcomes this time scale limitation and provides new insights into recognition of lipid transfer polyprotein by antibodies. In the future, this new and exciting development should see broad application to a range of tight macromolecular interactions.

Myosins generate force and motion by precisely coordinating their mechanical and chemical cycles, but the nature and timing of this coordination remains controversial. We utilized a FRET approach to examine the kinetics of structural changes in the force-generating lever arm in myosin V. We directly compared the FRET results with single-molecule mechanical events examined by optical trapping. We introduced a mutation (S217A) in the conserved switch I region of the active site to examine how myosin couples structural changes in the actin- and nucleotide-binding regions with force generation. Specifically, S217A enhanced the maximum rate of lever arm priming (recovery stroke) while slowing ATP hydrolysis, demonstrating that it uncouples these two steps. We determined that the mutation dramatically slows both actin-induced rotation of the lever arm (power stroke) and phosphate release (≥10-fold), whereas our simulations suggest that the maximum rate of both steps is unchanged by the mutation. Time-resolved FRET revealed that the structure of the pre– and post–power stroke conformations and mole fractions of these conformations were not altered by the mutation. Optical trapping results demonstrated that S217A does not dramatically alter unitary displacements or slow the working stroke rate constant, consistent with the mutation disrupting an actin-induced conformational change prior to the power stroke. We propose that communication between the actin- and nucleotide-binding regions of myosin assures a proper actin-binding interface and active site have formed before producing a power stroke. Variability in this coupling is likely crucial for mediating motor-based functions such as muscle contraction and intracellular transport.

RNA-protein interfaces control key replication events during the HIV-1 life cycle. The viral trans-activator of transcription (Tat) protein uses an archetypal arginine-rich motif (ARM) to recruit the host positive transcription elongation factor b (pTEFb) complex onto the viral trans-activation response (TAR) RNA, leading to activation of HIV transcription. Efforts to block this interaction have stimulated production of biologics designed to disrupt this essential RNA-protein interface. Here, we present four co-crystal structures of lab-evolved TAR-binding proteins (TBPs) in complex with HIV-1 TAR. Our results reveal that high-affinity binding requires a distinct sequence and spacing of arginines within a specific β2-β3 hairpin loop that arose during selection. Although loops with as many as five arginines were analyzed, only three arginines could bind simultaneously with major-groove guanines. Amino acids that promote backbone interactions within the β2-β3 loop were also observed to be important for high-affinity interactions. Based on structural and affinity analyses, we designed two cyclic peptide mimics of the TAR-binding β2-β3 loop sequences present in two high-affinity TBPs (KD values of 4.2 ± 0.3 and 3.0 ± 0.3 nm). Our efforts yielded low-molecular weight compounds that bind TAR with low micromolar affinity (KD values ranging from 3.6 to 22 μm). Significantly, one cyclic compound within this series blocked binding of the Tat-ARM peptide to TAR in solution assays, whereas its linear counterpart did not. Overall, this work provides insight into protein-mediated TAR recognition and lays the ground for the development of cyclic peptide inhibitors of a vital HIV-1 RNA-protein interaction.

V. G. Lysov
Trans. Moscow Math. Soc. 83 (), 291-304.
Abstract, references and article information

Duterte’s Victory Is Cry for Help From Those Left Behind in Philippines Expert comment sysadmin 12 May 2016

But large support for mainstream parties and a mature democratic system should keep the country from slipping back towards authoritarianism.

The victory of political outsider Rodrigo Duterte in the 2016 Philippines’ elections is proof that a significant minority of the country’s population feels left behind by its recent economic success and estranged from its political elite. However the results of the elections as a whole suggest that most voters opted for a continuation of the current government’s policies.

Duterte looks almost certain to be inaugurated as the next president of the Philippines on 30 June. The country’s presidential voting system – a single round, first-past-the-post election – delivered victory to a populist outsider with 39 per cent support. Two candidates advocating a continuation of the current government’s policies − the Liberal Party’s Mar Roxas and independent Grace Poe − polled a combined 45 per cent. The long-standing factionalism within Philippines elite politics split the ‘anti-Duterte’ vote.

Changing the conversation

The contrast between Duterte and Roxas could hardly be greater. Mar Roxas is the grandson of the first president of an independent Philippines, a graduate of Wharton Business School and a former investment banker in the US. Rodrigo Duterte is a political outsider with an electoral base geographically almost as far from Manila as is possible to get in the Philippines: the city of Davao on the island of Mindanao.

The story of Duterte’s victory is the story of how ‘Duterte managed to change the national conversation from poverty towards crime and corruption,’ says Marites Vitug, editor-at-large of one of the Philippines’ most popular online news sites, Rappler. In January, Duterte was running fourth in opinion polls but a strategy that positioned him as the only opponent to the Manila elite gave him victory. This is the first time a provincial official has made it to the top job.

The headline figures tell us that the Philippines’ economy has done very well under President Benigno Aquino. Between 2010 and 2014, growth averaged 6.3 per cent per year. That fell to a still-impressive 5.8 per cent last year but is expected to pick up this year and next, according to the Asian Development Bank. Growth in agriculture, however, is significantly slower and rural areas feel left behind. While economic growth is benefiting the majority, inequality is worsening and resentment rising in poor villages. The contrast between the metropolitan sophistication of the Makati district in Manila and life in faraway provinces such as Duterte’s Mindanao is widening.

Ironically the Philippines’ economic success is a part of the explanation for the defeat of the ‘mainstream’ presidential candidates. Crime and corruption may have become more important issues simply because more voters have become better off and therefore more likely to be concerned about crime and corruption than before. It’s also undeniable that Duterte has a record for getting things done. Human rights groups rightly criticize his (at best) tolerance of the extra-judicial killing of alleged criminals but his repeated re-election as mayor demonstrates that many citizens are prepared to accept that in exchange for improved personal security. A surprising number of Manila residents have actually moved to Davao because of its better quality of life.

Traditional power bases

However, the results as a whole suggest a narrow majority in favour of current policies. In the vice-presidential race, the Liberal Party candidate Leni Robredo is narrowly ahead of Ferdinand ‘Bongbong’ Marcos, the son of the eponymous former president. Like Duterte she is regarded as a successful mayor of a well-run city, Albay. Duterte’s running mate Alan Cayetano received just 14 per cent of the vote.

In the senate election, Liberals won five of the 12 seats being contested, with a party- backed independent winning a sixth. The opposition, even with boxing champion and national idol Manny Pacquiao running for the United Nationalist Alliance, won four.

Taken as a whole, the results show the enduring nature of traditional Philippines power bases. The country’s many islands and distinct linguistic and cultural regions are virtual fiefs in which families and big bosses can wield almost total power through control of local authorities, businesses, the courts and security forces.

Threat to democracy?

It’s easy to forget that the election of Ferdinand Marcos in 1965 was originally welcomed as a challenge to the traditional elites of Philippine politics. The same accolades are currently greeting Duterte. Could they presage a return to the Philippines’ bad old days?

This seems less likely. Philippine democracy has matured considerably since Marcos declared martial law in 1972. There is a substantial, and vocal, middle class with experience of mobilizing against ‘bad’ presidents. There will also be pressures from international investors and the Philippines’ treaty ally, the United States, for better governance.

The Philippines will chair the Association of Southeast Asian Nations next year. That will put Duterte in the international spotlight as host of several international meetings – including the East Asia Summit attended by, among others, the presidents of China, Russia and the US. Since his victory Duterte has promised to act with decorum in office and declared that his election campaign antics were just a ploy to attract attention. Some leaders in Southeast Asia will use his victory to buttress their arguments against allowing their people to freely vote. It’s up to Duterte to decide whether he wants to be an advertisement for – or an argument against – democracy.

To comment on this article, please contact Chatham House Feedback

Demographics and politics

Analysing political trends based on demographics is growing as the global population changes and traditional political affiliations are replaced.

Major issues for Chatham House research include the impact of the growth of young people in the developing world, significant increases in population aging in the developed world, and the impact of increasing urbanization on political engagement.

Gender and diversity also play an important part in changing political attitudes, while predicting voting behaviour is becoming ever harder to do accurately, as the methods and technology used by younger generations to engage with politics differ hugely from more traditional approaches.

Jan Goedgebeur, Jorik Jooken, On-Hei Solomon Lo, Ben Seamone and Carol T. Zamfirescu
Math. Comp. 93 (), 3059-3082.
Abstract, references and article information

Dr. Rekha Thomas from the University of Washington discusses three-dimensional image reconstructions from two-dimensional photos. The mathematics of image reconstruction is both simpler and more abstract than it seems. To reconstruct a 3D model based on photographic data, researchers and algorithms must solve a set of polynomial equations. Some solutions to these equations work mathematically, but correspond to an unrealistic scenario — for instance, a camera that took a photo backwards. Additional constraints help ensure this doesn't happen. Researchers are now investigating the mathematical structures underlying image reconstruction, and stumbling over unexpected links with geometry and algebra.

Nathan Brownlowe, Alcides Buss, Daniel Gonçalves, Jeremy B. Hume, Aidan Sims and Michael F. Whittaker
Trans. Amer. Math. Soc. 377 (), 5513-5560.
Abstract, references and article information

Víctor González-Aguilera, Alvaro Liendo, Pedro Montero and Roberto Villaflor Loyola
Trans. Amer. Math. Soc. 377 (), 5483-5511.
Abstract, references and article information

Noga Alon, Anurag Bishnoi, Shagnik Das and Alessandro Neri
Trans. Amer. Math. Soc. 377 (), 5389-5410.
Abstract, references and article information

Christoforos Neofytidis
Trans. Amer. Math. Soc. 377 (), 5289-5321.
Abstract, references and article information

dannyhennesy posted a photo:

On the Capital planet the rebellious droids had followed maily the Bat-Bot, but as time progressed his circuits had gone all mushy at 780 years or so without maintenance…

Several splinter groups all with their local bot leaders emerged such as the Che-bot, the traffic-light-robot and the Butt-bot, but none of these collected enough sentient circuits to call themselves a popular (or Animata) mass movement!

That was until a cyborg came along, one known as Jones, a long time prisoner and terrorist, his easy solutions to every problem rang well in the masses' auditory circuits!!!

His slogans and simple rhetoric were simple enough for the simple traffic-light to comprehend and cheer!

His language was full of hate towards the organics and especially the humans who were the most common races among the ruling class of the federation!!!

Despite being a “Fleshie” himself his message collected the angry enslaved
bot community by only weeks all rebellious robots except for a few fringe loonies had forgotten the old leaders…

One morning at Jones gave the signal…

All over the capital planet hordes and swarms of any form of mechanical sentient beings attacked first the police stations, then the Company boards running the planet and the federation as well as their starfleet…

Many died, especially the low level police and army! Many mechanicals died too, but their ranks were soon filled by Mutant fleshie allies of the lower levels who hated the Federation feudal society and upper classes as much as their technological allies…

The Federation state apparatus and ruling class, most of their fleet army fled when they knew the game was up, they activated the emergency escape plan and whole city blocks with important factories, administrational units, valuable assets and so on separated from the capital by hidden rocket engines and homed in their course to Mars…

On Mars the federation regrouped and formed their new society…

On the Capital planet, the robots proclaimed the first Techno-republic of the advanced inorganic civilization, the low level fleshies left behind, became slaves and their mutant allies got to rule their own minute chiefdoms as protectorates under the Techno-republic…

Jones was now the undisputed ruler of the capital planet, but the victory was a pyrros one since, all important buildings, all of value was now one Mars!

But as Jones put it:

Our proud race the Techno-species didn’t need the Fleshies administration, their infrastructure, their spaceships…

We shall start from scratch, with a new administration, a new order, every droid shall work at 4x speed than they did during human oppression since now we are free and the fleshies shall work twice as hard than the Techno-Race, until we have breed enough new fleshies so they can do all work!

Our future is bright and shiny like glistering shiny metal!

The snapshot seen here is from the first police station attacked in sector 45-34v-ss-g the first one to fall according to official techno-history!

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Designers note:

I am sad to say that this is the last episode in this years-spanning space series… At least for a while, I will still post LEGO hobby stuff here but without a storyline, perhaps small designs and builds… and occasionally a story when I feel like it!!!

I would like to thank all who had been in this journey of our heros, but it has taken far to much time and effort and since the state of the world is as it is, I am spiraling down in another depression, I must stop it before I reach the abyss, so I have remove some stress out of my equation… I ended it in a cliffhanger so I can easily restart it when my mental health improves… I hope that won’t be forever???

I would love if someone used my characters or ideas, please send me a link if you do, I would love to read it or look at it!!!

But there will be more Lego, just in different format without long stories, I need to focus more on my art and to be honest that is the only time the mental pain eases, when I create!!!


Peace and Noise!

MushroomBrain a FOL