23 January 2020

The project purpose is to ensure emissions reduction and resilience strategies, policies and decision-making - both in China and globally - are better informed by an evidence-based perspective on climate-change risks.

The actin cytoskeleton is extremely dynamic and supports diverse cellular functions in many physiological and pathological processes, including tumorigenesis. However, the mechanisms that regulate the actin-related protein 2/3 (ARP2/3) complex and thereby promote actin polymerization and organization in cancer cells are not well-understood. We previously implicated the proline-rich 11 (PRR11) protein in lung cancer development. In this study, using immunofluorescence staining, actin polymerization assays, and siRNA-mediated gene silencing, we uncovered that cytoplasmic PRR11 is involved in F-actin polymerization and organization. We found that dysregulation of PRR11 expression results in F-actin rearrangement and nuclear instability in non-small cell lung cancer cells. Results from molecular mechanistic experiments indicated that PRR11 associates with and recruits the ARP2/3 complex, facilitates F-actin polymerization, and thereby disrupts the F-actin cytoskeleton, leading to abnormal nuclear lamina assembly and chromatin reorganization. Inhibition of the ARP2/3 complex activity abolished irregular F-actin polymerization, lamina assembly, and chromatin reorganization due to PRR11 overexpression. Notably, experiments with truncated PRR11 variants revealed that PRR11 regulates F-actin through different regions. We found that deletion of either the N or C terminus of PRR11 abrogates its effects on F-actin polymerization and nuclear instability and that deletion of amino acid residues 100–184 or 100–200 strongly induces an F-actin structure called the actin comet tail, not observed with WT PRR11. Our findings indicate that cytoplasmic PRR11 plays an essential role in regulating F-actin assembly and nuclear stability by recruiting the ARP2/3 complex in human non-small cell lung carcinoma cells.

Knowledge of the molecular events in mitochondrial DNA (mtDNA) replication is crucial to understanding the origins of human disorders arising from mitochondrial dysfunction. Twinkle helicase is an essential component of mtDNA replication. Here, we employed atomic force microscopy imaging in air and liquids to visualize ring assembly, DNA binding, and unwinding activity of individual Twinkle hexamers at the single-molecule level. We observed that the Twinkle subunits self-assemble into hexamers and higher-order complexes that can switch between open and closed-ring configurations in the absence of DNA. Our analyses helped visualize Twinkle loading onto and unloading from DNA in an open-ringed configuration. They also revealed that closed-ring conformers bind and unwind several hundred base pairs of duplex DNA at an average rate of ∼240 bp/min. We found that the addition of mitochondrial single-stranded (ss) DNA–binding protein both influences the ways Twinkle loads onto defined DNA substrates and stabilizes the unwound ssDNA product, resulting in a ∼5-fold stimulation of the apparent DNA-unwinding rate. Mitochondrial ssDNA-binding protein also increased the estimated translocation processivity from 1750 to >9000 bp before helicase disassociation, suggesting that more than half of the mitochondrial genome could be unwound by Twinkle during a single DNA-binding event. The strategies used in this work provide a new platform to examine Twinkle disease variants and the core mtDNA replication machinery. They also offer an enhanced framework to investigate molecular mechanisms underlying deletion and depletion of the mitochondrial genome as observed in mitochondrial diseases.

Cas12a (Cpf1) is an RNA-guided endonuclease in the bacterial type V-A CRISPR-Cas anti-phage immune system that can be repurposed for genome editing. Cas12a can bind and cut dsDNA targets with high specificity in vivo, making it an ideal candidate for expanding the arsenal of enzymes used in precise genome editing. However, this reported high specificity contradicts Cas12a's natural role as an immune effector against rapidly evolving phages. Here, we employed high-throughput in vitro cleavage assays to determine and compare the native cleavage specificities and activities of three different natural Cas12a orthologs (FnCas12a, LbCas12a, and AsCas12a). Surprisingly, we observed pervasive sequence-specific nicking of randomized target libraries, with strong nicking of DNA sequences containing up to four mismatches in the Cas12a-targeted DNA-RNA hybrid sequences. We also found that these nicking and cleavage activities depend on mismatch type and position and vary with Cas12a ortholog and CRISPR RNA sequence. Our analysis further revealed robust nonspecific nicking of dsDNA when Cas12a is activated by binding to a target DNA. Together, our findings reveal that Cas12a has multiple nicking activities against dsDNA substrates and that these activities vary among different Cas12a orthologs.

In bacteria, the restart of stalled DNA replication forks requires the DNA helicase PriA. PriA can recognize and remodel abandoned DNA replication forks, unwind DNA in the 3'-to-5' direction, and facilitate the loading of the helicase DnaB onto the DNA to restart replication. Single-stranded DNA–binding protein (SSB) is typically present at the abandoned forks, but it is unclear how SSB and PriA interact, although it has been shown that the two proteins interact both physically and functionally. Here, we used atomic force microscopy to visualize the interaction of PriA with DNA substrates with or without SSB. These experiments were done in the absence of ATP to delineate the substrate recognition pattern of PriA before its ATP-catalyzed DNA-unwinding reaction. These analyses revealed that in the absence of SSB, PriA binds preferentially to a fork substrate with a gap in the leading strand. Such a preference has not been observed for 5'- and 3'-tailed duplexes, suggesting that it is the fork structure that plays an essential role in PriA's selection of DNA substrates. Furthermore, we found that in the absence of SSB, PriA binds exclusively to the fork regions of the DNA substrates. In contrast, fork-bound SSB loads PriA onto the duplex DNA arms of forks, suggesting a remodeling of PriA by SSB. We also demonstrate that the remodeling of PriA requires a functional C-terminal domain of SSB. In summary, our atomic force microscopy analyses reveal key details in the interactions between PriA and stalled DNA replication forks with or without SSB.

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.

Histone H2B monoubiquitylation (H2Bub1) has central functions in multiple DNA-templated processes, including gene transcription, DNA repair, and replication. H2Bub1 also is required for the trans-histone regulation of H3K4 and H3K79 methylation. Although previous studies have elucidated the basic mechanisms that establish and remove H2Bub1, we have only an incomplete understanding of how H2Bub1 is regulated. We report here that the histone H4 basic patch regulates H2Bub1. Yeast cells with arginine-to-alanine mutations in the H4 basic patch (H42RA) exhibited a significant loss of global H2Bub1. H42RA mutant yeast strains also displayed chemotoxin sensitivities similar to, but less severe than, strains containing a complete loss of H2Bub1. We found that the H4 basic patch regulates H2Bub1 levels independently of interactions with chromatin remodelers and separately from its regulation of H3K79 methylation. To measure H2B ubiquitylation and deubiquitination kinetics in vivo, we used a rapid and reversible optogenetic tool, the light-inducible nuclear exporter, to control the subcellular location of the H2Bub1 E3 ligase, Bre1. The ability of Bre1 to ubiquitylate H2B was unaffected in the H42RA mutant. In contrast, H2Bub1 deubiquitination by SAGA-associated Ubp8, but not by Ubp10, increased in the H42RA mutant. Consistent with a function for the H4 basic patch in regulating SAGA deubiquitinase activity, we also detected increased SAGA-mediated histone acetylation in H4 basic patch mutants. Our findings uncover that the H4 basic patch has a regulatory function in SAGA-mediated histone modifications.

What President Trump calls a border crisis is in fact a crisis in the asylum system—one worsened at every turn by his administration’s harsh policies and rhetoric. Rather than spend $5.7 billion on a wall, it would be far more effective to use the money to retool an overwhelmed asylum system, adapt outmatched border enforcement infrastructure to respond to the changing composition of arrivals, and work cooperatively with Mexico to tackle the factors propelling Central Americans to flee.

The House is set to vote on two bills that would largely dismantle the U.S. asylum system at the southern border by significantly narrowing grounds to apply for asylum, eliminating protections for the vast majority of unaccompanied minors, and unilaterally declaring Mexico a safe third country. The result would be a sharp reduction in the number of people permitted to seek humanitarian protection, as this commentary explains.

President Trump has made reshaping the U.S. immigration system a top priority. Yet the fragmented nature of policy-making in the United States—with power split between branches and levels of government—has made it difficult to pursue some of his most ambitious proposals. This report explores the evolution of migration policy under Trump, and what these changes may mean in the long run.

A report release and presentation of first-ever U.S. estimates on the actual economic costs of skill underutilization for immigrants, their families, and the U.S. economy, in terms of forgone earnings and unrealized federal, state, and local taxes.

Over the past decade, immigrant investor programs have proliferated around the world, and Chinese applicants have dominated in a number of countries. In 2015, about 9,000 Chinese millionaires moved to other countries, many through so-called golden visa programs. This article explores the social and cultural factors driving well-off Chinese to move abroad and examines perceptions of elite emigration in China.

The immigrant population in the Kansas City region has grown rapidly over the past 25 years, contributing to overall population growth in the area. This fact sheet describes immigrants in the metro area, examining their origins, industries of employment, income and poverty levels, English proficiency, educational attainment, and more.

China has been Africa’s largest trading partner since 2009, and as commerce and investment have increased, so have flows of people in both directions. With an estimated 1 million to 2 million Chinese migrants across Africa, some countries have relaxed their short-term visa requirements in hopes of facilitating cultural and business exchanges. High levels of Chinese investment do not, however, correlate with more liberal visa policies, as this article explores.

Large outflows of educated young people escaping high levels of unemployment, in tandem with inflows of unauthorized migrants, pose a fresh set of challenges for Greek policymakers. This Transatlantic Council on Migration report examines Greek emigration, and its economic implications, before exploring policy directions to minimize the costs and maximize the benefits of this mobility.

The Armenian diaspora, which significantly exceeds the country's resident population, has played an instrumental role in Armenia's political and economic development since independence in 1991. Yet a picture emerges of divergent currents within the diaspora, often seen from above as a unified entity. Delve into differences in engagement among Armenia's "old" and "new" diasporas with this feature article.

With many countries in East Asia facing unfavorable demographic shifts in the form of aging populations, low fertility, and shrinking workforces, governments in 2016 continued to explore immigration as a potential policy solution. However, a tradition of cultural homogeneity and wariness among publics about increased immigration is leading policymakers to test the waters with very small steps.

In the face of an uptick in unauthorized arrivals in Italy from Tunisia in 2017, the European Union dusted off earlier policy proposals such as funding to increase Tunisia’s border-control capabilities and the creation of disembarkation platforms. This article explores why contemporary developments, including a fragile Tunisian political system, suggest the need for a different approach.

Bangladeshis in 2017 suddenly emerged as one of the top migrant groups entering Europe illegally. While Europe is a new destination, Bangladeshi labor migration has been an important part of the country's development since the 1970s, with growing numbers heading abroad, largely to the Gulf Cooperation Council countries. This article explores and contextualizes the new phenomenon of Bangladeshi migration to Europe.

Governments on the receiving end of migrants and refugees reinforced their commitment to returns in 2017, sending or coercing migrants to move back to impoverished or violent homelands. The Dominican Republic pushed out some 70,000 Haitians and native born of Haitian descent, while more than 500,000 Afghans left Iran and Pakistan. Though many of these migrants chose to return, in practice the line between forced and voluntary returns is blurry.

As the final phase of preparations for the historic adoption of a Global Compact for Safe, Orderly, and Regular Migration approaches, this webinar explores two central objectives of the compact: enhancing the availability and flexibility of pathways for regular migration, and investing in skills development. 

As the final phase of preparations for the historic adoption of a Global Compact for Safe, Orderly, and Regular Migration approaches, this webinar explores two central objectives of the compact: enhancing the availability and flexibility of pathways for regular migration, and investing in skills development.

Authoritarian states have long attempted to restrict citizens’ movement. But what happens when their reach extends beyond their borders? The October 2018 assassination of Saudi journalist Jamal Khashoggi brought into sharp relief the long arm of these regimes in reaching citizens abroad. This phenomenon, “transnational authoritarianism,” further shows that the relationship between migration and authoritarianism is becoming more complex.

Although long one of the world's top migrant destinations, only in the recent past has Germany come to acknowledge and adjust to its role as a country of immigration. Its welcoming approach—a relatively new development—has been put to the test amid massive humanitarian inflows beginning in 2015. This country profile examines Germany's history on immigration and highlights current and emerging debates.

One of the most rapidly aging societies in the world, Japan is looking to immigration to address increased labor shortages—albeit slowly and largely without public debate. This country profile offers a brief overview of Japan’s migration history and examines the current immigration system, in particular policies and programs to bring in foreign workers, particularly on a temporary basis.

Colombia has more internally displaced persons (IDPs) than any other country in the world, the result of a 52-year civil war. Beyond improving the lives of its 7.3 million IDPs, the country faces a number of crucial migration issues as it works to achieve stability in the wake of an historic peace accord signed in late 2016. This country profile examines historical trends and current and future migration challenges in Colombia.

From being a source of labor emigration to the Gulf region to a destination for refugees from Syria, sub-Saharan Africa, and elsewhere, Egypt has long experienced different forms of mobility. This article, which profiles the trends and policies that have shaped Egypt's migration history, focuses on its long-standing use of migration as a soft-power tool to achieve its foreign policy aims and as a safety valve for political discontent.

El Salvador is the smallest country in Central America yet the most densely populated. A stagnant economy, high levels of crime and violence, and natural disasters have pushed growing numbers of people to migrate without authorization or seek asylum abroad, mostly in the United States. This article explores historical and contemporary emigration from El Salvador.

This policy brief explores the relationship between environmental change and migration to Europe in light of recent scholarship challenging the notion that environmental change triggers mass migration. It presents an overview of European policy response in this area and summarizes the spectrum of proposed solutions.

Even as Nepal will lean more heavily on its international diaspora to help recover from devastating earthquakes that killed thousands and decimated parts of the country, the disasters have had effects on internal migration. Class and gender dynamics have long driven significant internal flows. This feature article explores migration trends in Nepal, including movement between ecological zones, growing urbanization, and the feminization of an increasingly mobile workforce.

From earthquakes to drought, natural disasters and climate change played a key role in migration flows in 2015. Climate-induced migration surfaced as a concern at the United Nations Climate Change Conference (known as COP21) as international organizations and policymakers have begun to recognize the growing challenges, and potential protection obligations, of such movement.

Migrants displaced by crisis do not benefit from international protection the way that refugees do. This article examines the experiences of labor migrants amid manmade and natural disasters in the Central African Republic, Côte d’Ivoire, Lebanon, Libya, South Africa, and Thailand, as well as stakeholder responses. Research demonstrates the agency and resilience of migrants, who develop flexible solutions in the face of crisis.

This report by MPI and the Asian Development Bank lays out a realistic roadmap toward freer movement among skilled professionals within the ASEAN Economic Community (AEC), encouraging cooperation among ASEAN Member States in recognizing foreign qualifications and making government investments in training and educations systems that prepare workers in accordance with common standards.

This report discusses Spain’s changing migration patterns in the wake of dramatic economic downturn, paying special attention to the effects of the emigration of young, native-born Spaniards. The report also focuses on policies geared toward engaging the increasing number of Spaniards abroad, finding that much of Spain's policy towards diasporas predates the 1980s.

Given diverging demographics, rising educational attainment and wide variation in economic opportunities, countries in the Association of Southeast Asian Nations are poised to see an expansion of both the demand for and supply of skilled migrants willing and able to move. The convergence of these megatrends represents unique opportunities for human-capital development and brain circulation, as this report explores.

While it has been years since the Association of Southeast Asian Nations signed accords to facilitate the movement of professionals in seven occupations, implementation of these Mutual Recognition Arrangements remains "painfully slow and uneven across countries." This final report in an MPI-Asian Development Bank series explores MRA implementation by sector, and offers recommendations to help achieve the goal of greater skill mobility in Southeast Asia.

A discussion, including the former United Nations Deputy High Commissioner for Refugees, examining the huge strains on the global protection system and how it can better respond to protracted refugee situations and other long-term displacement, focusing on the conclusions of the Transatlantic Council on Migration's recent meeting, Beyond Asylum: Rethinking Protection Policies to Meet Sharply Escalating Needs.

An MPI Leadership Visions discussion with the Foreign Minister of Mexico, Claudia Ruiz-Massieu, for her first public appearance in Washington, DC. 

Una llamada en español que analiza las dinámicas cambiantes y las cuestiones políticas relacionadas con la migración a través de México a los Estados Unidos.