title: Chronic DNA Replication Stress Reduces Replicative Lifespan of Cells by TRP53-Dependent, microRNA-Assisted MCM2-7 Downregulation.
abstract: Circumstances that compromise efficient DNA replication, such as disruptions to replication fork progression, cause a state known as DNA replication stress (RS). Whereas normally proliferating cells experience low levels of RS, excessive RS from intrinsic or extrinsic sources can trigger cell cycle arrest and senescence. Here, we report that a key driver of RS-induced senescence is active downregulation of the Minichromosome Maintenance 2-7 (MCM2-7) factors that are essential for replication origin licensing and which constitute the replicative helicase core. Proliferating cells produce high levels of MCM2-7 that enable formation of dormant origins that can be activated in response to acute, experimentally-induced RS. However, little is known about how physiological RS levels impact MCM2-7 regulation. We found that chronic exposure of primary mouse embryonic fibroblasts (MEFs) to either genetically-encoded or environmentally-induced RS triggered gradual MCM2-7 repression, followed by inhibition of replication and senescence that could be accelerated by MCM hemizygosity. The MCM2-7 reduction in response to RS is TRP53-dependent, and involves a group of Trp53-dependent miRNAs, including the miR-34 family, that repress MCM expression in replication-stressed cells before they undergo terminal cell cycle arrest. miR-34 ablation partially rescued MCM2-7 downregulation and genomic instability in mice with endogenous RS. Together, these data demonstrate that active MCM2-7 repression is a physiologically important mechanism for RS-induced cell cycle arrest and genome maintenance on an organismal level.
authors.affiliation: Department of Biomedical Sciences, Cornell University, Ithaca, New York, United States of America.|Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America.
authors.forename: Gongshi
authors.initials: G
authors.lastname: Bai
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America.|Weill Institute for Cellular and Molecular Biology, Cornell University, Ithaca, New York, United States of America.|Center for Vertebrate Genomics, Cornell University, Ithaca, New York, United States of America.
authors.forename: Marcus B
authors.initials: MB
authors.lastname: Smolka
authors.affiliation: Department of Biomedical Sciences, Cornell University, Ithaca, New York, United States of America.|Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America.|Center for Vertebrate Genomics, Cornell University, Ithaca, New York, United States of America.
authors.forename: John C
authors.initials: JC
authors.lastname: Schimenti
mesh_terms: D000818:Animals; D059447:Cell Cycle Checkpoints / Q000235:genetics; D049109:Cell Proliferation / Q000235:genetics; D004261:DNA Replication / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D042822:Genomic Instability; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D064110:Minichromosome Maintenance Proteins / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C551848:MIRN34a microRNA, mouse; D035683:MicroRNAs; D064110:Minichromosome Maintenance Proteins