ABSTRACT
Resistance to regeneration of insulin-producing pancreatic ß 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 ß cells to proliferate, but their detailed mechanism of action is incompletely understood. We interrogated our human insulinoma and ß cell transcriptomic databases seeking to understand why ß cells in insulinomas proliferate, while normal ß cells do not. This search reveals the DREAM complex as a central regulator of quiescence in human ß 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 ß cells to replicate by converting the repressive DREAM complex to its pro-proliferative MMB conformation.
Subject(s)
Diabetes Mellitus, Type 2 , Insulin-Secreting Cells , Insulinoma , Pancreatic Neoplasms , Adult , Cell Proliferation , Humans , Insulin-Secreting Cells/metabolism , Insulinoma/genetics , Protein Serine-Threonine Kinases/genetics , Protein-Tyrosine Kinases/metabolismABSTRACT
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.
Subject(s)
Antineoplastic Agents/pharmacology , Carcinoma, Non-Small-Cell Lung/drug therapy , Cell Cycle Proteins/metabolism , Checkpoint Kinase 1/antagonists & inhibitors , Forkhead Box Protein M1/metabolism , Lung Neoplasms/drug therapy , Mitosis/drug effects , Protein Kinase Inhibitors/pharmacology , Pyrazines/pharmacology , Pyrazoles/pharmacology , Trans-Activators/metabolism , A549 Cells , Carcinoma, Non-Small-Cell Lung/enzymology , Carcinoma, Non-Small-Cell Lung/genetics , Carcinoma, Non-Small-Cell Lung/pathology , Cell Cycle Checkpoints/drug effects , Cell Cycle Proteins/genetics , Checkpoint Kinase 1/genetics , Checkpoint Kinase 1/metabolism , Forkhead Box Protein M1/genetics , Gene Expression Regulation, Neoplastic , Humans , Lung Neoplasms/enzymology , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Multiprotein Complexes , Signal Transduction , Trans-Activators/geneticsABSTRACT
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.
