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.

As the U.S. health-care system sags under the strain of the COVID-19 pandemic, health-care workers are not only on the frontlines fighting the virus, they are also some of the most at-risk individuals, making it more essential than ever to have sufficient numbers of qualified health professionals. While 1.5 million immigrants and refugees are already working in the U.S. health-care system, an additional 263,000 immigrants and refugees in the U.S. with health-related college degrees are working in low-skilled jobs or are out of work.

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.

More than 1 million international students were in the United States in 2015-16, a significant share of them in science, technology, engineering, or math (STEM) fields. While countries increasingly are vying for this population, these individuals face a complex choice upon graduation: to stay or leave? This article examines international STEM students in the United States and the motivations underlying their postgraduation plans.

Though small, the population of Canadians in the United States is quite diverse, and includes students, highly skilled professionals on H-1B or NAFTA visas, family migrants, and retirees. Canadian immigrants have much higher educational attainment and incomes than the native- and overall foreign-born populations. This article offers an interesting data snapshot of Canadians in the United States.

The Trump administration’s decision to terminate the Deferred Action for Childhood Arrivals (DACA) deportation-relief program launched in 2012 has sparked new urgency to find a longer-term fix for "DREAMers," the unauthorized immigrants brought to the United States as children. This Policy Beat article examines movement in the courts and in Congress on the DREAM Act and similar proposals, exploring likely paths forward.

In its first year, the Trump administration moved to deliver on some of Donald Trump’s campaign promises on immigration, including ramping up enforcement in the U.S. interior and ending the Deferred Action for Childhood Arrivals (DACA) program. The administration also announced the termination of Temporary Protected Status (TPS) for nationals of some countries. This article explores some of the top policy changes.

Discussion at this event focused on findings from MPI's report examining the interior immigration enforcement system in the United States, including ICE data on deportations and arrests, and the responses of state and local governments, civil society, and consulates.  

Experts on this Spanish language webinar examine the operation of today’s interior immigration enforcement system and how state and local governments, civil society, and consulates are responding.    

This fact sheet uses U.S. and Mexican apprehensions data to trace the evolving trends in unaccompanied child and family migration from Central America through Mexico and to the United States, and discusses the push factors and pull factors responsible for the increase in flows seen in recent years, as well as the growing role of smuggling organizations.

Citizenship and integration policies are often thought of as markers for whether a country is welcoming to immigrants. Yet research suggests that public opinion and political rhetoric play a bigger role in immigrants' sense of belonging. This article explores how boundaries between "us" and "them" are drawn through popular conceptions of nationhood and political rhetoric, and their impact on immigrants' belonging.

Marking the release of an MPI report, this discussion focuses on the dynamics in low-wage workplaces and immigration law that have contributed to systematic violations of labor standards and explores new and effective enforcement strategies that state and local governments across the United States are utilizing.

This discussion, featuring California's Labor Commissioner and the head of the Tennessee Bureau of Workers' Compensation, launched a report that examines state innovations in labor standards enforcement in low-wage, immigrant-dense industries. With wage underpayment, payroll fraud, and other violations widespread in industries such as construction and car-washing, the discussion focused on how targeted enforcement can deter practices that hurt native-born and immigrant workers alike, cost state tax revenue, and disadvantage law-abiding employers. 

Marking the release of an MPI study, this discussion examines the operation of today’s interior enforcement system and how state and local governments, civil society, and consulates are responding.    

A Spanish language webinar examining the operation of today’s interior enforcement system and how state and local governments, civil society, and consulates are responding.    

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.

With more than 3 million Venezuelans having fled their country in crisis, this event features the release of an MPI-OAS report that examines the creative responses that host countries in Latin America are providing. These include the opening of legal pathways to residence, access to formal labor markets, and greater use of forms of ID for recognition.

Convocamos un seminario en línea (webinar) en español en la ocasión del lanzamiento del informe, Creatividad dentro de la crisis: opciones legales para inmigrantes venezolanos en América Latina, que describe donde se han radicado los migrantes venezolanos; las medidas que han utilizado los gobiernos latinoamericanos para regularizar el estatus legal de los migrantes venezolanos; y los esfuerzos por integrar a los recién llegados en sus nuevas comunidades de residencia.

This discussion on the 1986 Immigration Reform and Control Act (IRCA) showcases MPI Fellow Charles Kamasaki's book, Immigration Reform: The Corpse That Will Not Die. Kamasaki is joined by other veterans of the IRCA debate for a conversation on the lessons, the intended and unintended consequences, and how the law’s legacy has shaped contemporary politics on immigration.

Long a country of emigration and a springboard for migrants aiming to reach Europe, Morocco has emerged as a destination for many sub-Saharan Africans. As more migrants remain in Morocco, the kingdom has implemented policies to aid with integration. But challenges remain, with most of the estimated 700,000 sub-Saharan Africans living in precarious conditions and irregular status despite some legalization programs.

This event focuses on the changing face of Mexican migration to the United States, Mexican immigrants' contributions to U.S. society and political and economic power, as well as that of those who have returned to Mexico.

While the Global Compact for Safe, Orderly, and Regular Migration was formally adopted by 164 of the UN's 193 Member States, it's worth asking how it became a point of contention and ultimately was rejected by more than a dozen countries. The answer? A long lag time between negotiation and adoption, during which overheated claims against it went largely unanswered, as this commentary explores.

Development assistance may be a blunt tool for reshaping migration patterns—and indeed one that could increase flows over the short term. Shifting the focus away from increasing individuals’ skills and assets toward investments in the broader economic or governance structures that are a prerequisite for growth and stability may offer more alternatives to emigration in the long run.

With a history of encouraging workers to emigrate to relieve unemployment at home, Tunisia now has 11 percent of its population living abroad. The factors underlying the 2011 revolution that sparked the Arab Spring have also fueled emigration desires for many Tunisians. This country profile explores historical and current trends in Tunisia from colonial settlement to the aftermath of the Arab Spring, and the new focus on migrant rights at home and abroad.

Faced with labor shortages in key sectors of the economy, South Korea has moved carefully in recent decades toward accepting greater numbers of workers—albeit in temporary fashion. Its Employment Permit System, launched in 2003, earned international accolades for bringing order and legality to immigration in the country, although several challenges remain to be addressed as this Country Profile explores.

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.

Nearly 50,000 asylum seekers have entered Canada irregularly via land crossing from the United States since spring 2017—contributing to a doubling in the overall number of asylum requests seen in 2016. Based on interviews with asylum claimants, this article analyzes their motivations for making the journey and the political implications of rising irregular migration to Canada.

This report summarizes the economic and social development policy achievements of Central American countries over the past 20 years, as well as the notable obstacles to development that remain. The author identifies long-term challenges and outlines how they can be incorporated into a new development agenda.

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.

While skilled migration brings widely acknowledged economic benefits for destination countries and migrants, its impact on countries of origin has been the subject of more debate. Despite a growing consensus that origin countries can benefit from emigration and the circulation of skills, enabling this potential to be fully exploited remains a challenge. This report examines initiatives that develop skills and human capital.

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 event with UN High Commissioner for Refugees António Guterres includes a discussion on the state of citizen security in Central America and the resulting humanitarian impact, featuring findings from Children on the Run, a UNHCR report based on interviews with more than 400 unaccompanied children from the region.

Amid aging populations and the growth of chronic diseases, the demand for skilled health-care professionals is on the rise in the United States, Canada, and Mexico. This report explores the policy implications, benefits, and challenges of harmonizing nursing qualifications in the region, suggesting that a more collaborative approach could result in greater supply and quality of nurses.

This report examines the rising numbers of apprehensions and deportations of Central American children and adults by the United States and Mexico, and provides a demographic, socioeconomic, and criminal profile of deportees to El Salvador, Guatemala, and Honduras. The report traces how rising Mexican enforcement is reshaping regional dynamics and perhaps ushering in changes to long-lasting trends in apprehensions.

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

A webinar releasing a report examining deportations to Central America and reception and reintegration services in El Salvador, Guatemala, and Honduras.

For a growing population of migrants deported from Mexico and the United States to Central America, the conditions upon return typically are worse than when they left, setting up a revolving-door cycle of migration, deportation, and remigration. This report provides a detailed profile of reception and reintegration services offered in El Salvador, Guatemala, and Honduras to deported migrants, examining their challenges and opportunities for improvement. 

A webinar releasing a report examining deportations to Central America and reception and reintegration services in El Salvador, Guatemala, and Honduras.

Mexican immigration to the United States has slowed in recent years, and since the Great Recession more Mexican immigrants have returned to Mexico than have migrated to the United States. Mexicans, however, remain the largest origin group in the country, accounting for 28 percent of all immigrants. See how Mexican immigrants compare to the overall foreign- and U.S.-born populations on key indicators with this Spotlight article.