The ability to shut off host gene expression is a shared feature of many viral infections, and it is thought to promote viral replication by freeing host cell machinery and blocking immune responses. Despite the molecular differences between viruses, an emerging theme in the study of host shutoff is that divergent viruses use similar mechanisms to enact host shutoff. Moreover, even viruses that encode few proteins often have multiple mechanisms to affect host gene expression, and we are only starting to understand how these mechanisms are integrated. In this review we discuss the multiplicity of host shutoff mechanisms used by the orthomyxovirus influenza A virus and members of the alpha- and gamma-herpesvirus subfamilies. We highlight the surprising similarities in their mechanisms of host shutoff and discuss how the different mechanisms they use may play a coordinated role in gene regulation.

SUMMARY To identify genes whose loss confers resistance to CHK1 inhibitors, we perform genome-wide CRISPR-Cas9 screens in non-small-cell lung cancer (NSCLC) cell lines treated with the CHK1 inhibitor prexasertib (CHK1i). Five of the top six hits of the screens, MYBL2 (B-MYB), LIN54, FOXM1, cyclin A2 (CCNA2), and CDC25B, are cell-cycle-regulated genes that contribute to entry into mitosis. Knockout of MMB-FOXM1 complex components LIN54 and FOXM1 reduce CHK1i-induced DNA replication stress markers and premature mitosis during Late S phase. Activation of a feedback loop between the MMB-FOXM1 complex and CDK1 is required for CHK1i-induced premature mitosis in Late S phase and subsequent replication catastrophe, indicating that dysregulation of the S to M transition is necessary for CHK1 inhibitor sensitivity. These findings provide mechanistic insights into small molecule inhibitors currently studied in clinical trials and provide rationale for combination therapies.

Resistance to regeneration of insulin-producing pancreatic β cells is a fundamental challenge for type 1 and type 2 diabetes. Recently, small molecule inhibitors of the kinase DYRK1A have proven effective in inducing adult human β cells to proliferate, but their detailed mechanism of action is incompletely understood. We interrogated our human insulinoma and β cell transcriptomic databases seeking to understand why β cells in insulinomas proliferate, while normal β cells do not. This search reveals the DREAM complex as a central regulator of quiescence in human β cells. The DREAM complex consists of a module of transcriptionally repressive proteins that assemble in response to DYRK1A kinase activity, thereby inducing and maintaining cellular quiescence. In the absence of DYRK1A, DREAM subunits reassemble into the pro-proliferative MMB complex. Here, we demonstrate that small molecule DYRK1A inhibitors induce human β cells to replicate by converting the repressive DREAM complex to its pro-proliferative MMB conformation.

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17The tight control of viral and host gene expression is critical to the replication of herpesviruses, 18 including the gamma-herpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV). While 19 some of the KSHV proteins that contribute to viral and host gene regulation are known, it is clear 20 that there are additional uncharacterized contributing viral factors. Identifying these proteins and 21 their role in gene regulation is important to determine the mechanistic underpinnings of the 22 complex replication cycle of KSHV. Through a reporter-based screen, we have identified several 23 new potential KSHV-encoded gene regulators, including the previously uncharacterized protein 24 ORF42, which we find stimulates global protein production upon overexpression. We have 25 generated an ORF42-null virus, which revealed that ORF42 is required for wild-type levels of 26 virus production. Moreover, global protein synthesis and the accumulation of viral proteins are 27 reduced in infected cells in the absence of ORF42, suggesting that ORF42 regulates protein 28 synthesis during infection. A comparison of the effects of ORF42 on the levels of RNA and 29 protein suggests that ORF42 acts post-transcriptionally to control protein levels. In addition to 30 gene regulation, ORF42 may have other functions in virion formation, as it is found in viral 31 particles, which is consistent with the described roles of the ORF42 homologs in alpha-and beta-32 herpesviruses. 33 3 Importance 34 Kaposi's sarcoma-associated herpesvirus (KSHV) causes Kaposi's sarcoma, an AIDS-associated 35 malignancy that remains one of the leading causes of cancer deaths in sub-Saharan Africa. 36 Replication of the virus is important for tumor formation and inhibition of viral replication may 37 be used for treatment. The correct levels and temporal expression of viral and host genes during 38 KSHV replication are key to viral replication, but the mechanisms that control this regulation 39 remain enigmatic. Here we identify several new KSHV proteins involved in viral and cellular 40 gene regulation and characterize the previously unstudied KSHV ORF42 protein in regulation of 41 viral and host protein levels and efficient formation of viral progeny. 42 4 Introduction 43

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