title: Smc5/6-mediated regulation of replication progression contributes to chromosome assembly during mitosis in human cells.
abstract: The structural maintenance of chromosomes (SMC) proteins constitute the core of critical complexes involved in structural organization of chromosomes. In yeast, the Smc5/6 complex is known to mediate repair of DNA breaks and replication of repetitive genomic regions, including ribosomal DNA loci and telomeres. In mammalian cells, which have diverse genome structure and scale from yeast, the Smc5/6 complex has also been implicated in DNA damage response, but its further function in unchallenged conditions remains elusive. In this study, we addressed the behavior and function of Smc5/6 during the cell cycle. Chromatin fractionation, immunofluorescence, and live-cell imaging analyses indicated that Smc5/6 associates with chromatin during interphase but largely dissociates from chromosomes when they condense in mitosis. Depletion of Smc5 and Smc6 resulted in aberrant mitotic chromosome phenotypes that were accompanied by the abnormal distribution of topoisomerase IIα (topo IIα) and condensins and by chromosome segregation errors. Importantly, interphase chromatin structure indicated by the premature chromosome condensation assay suggested that Smc5/6 is required for the on-time progression of DNA replication and subsequent binding of topo IIα on replicated chromatids. These results indicate an essential role of the Smc5/6 complex in processing DNA replication, which becomes indispensable for proper sister chromatid assembly in mitosis.
authors.affiliation: Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan Bio-Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8501, Japan Cancer Institute, Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, Tokyo 102-0076, Japan.
authors.forename: Lina Marcela
authors.initials: LM
authors.lastname: Gallego-Paez
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanaka
authors.forename: Masashige
authors.initials: M
authors.lastname: Bando
authors.forename: Motoko
authors.initials: M
authors.lastname: Takahashi
authors.forename: Naohito
authors.initials: N
authors.lastname: Nozaki
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Nakato
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Shirahige
authors.forename: Toru
authors.initials: T
authors.lastname: Hirota
mesh_terms: D000951:Antigens, Neoplasm / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics*; D002843:Chromatin / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone; D020090:Chromosome Segregation / Q000235:genetics; D022004:Chromosome Structures / Q000737:chemistry / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D008938:Mitosis / Q000235:genetics*; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics
chemical_list: D000951:Antigens, Neoplasm; D018797:Cell Cycle Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; C432931:SMC5 protein, human; C432932:SMC6 protein, human; D004250:DNA Topoisomerases, Type II