title: Cell cycle-dependent regulation of a human DNA helicase that localizes in DNA damage foci.
abstract: Mutational studies of human DNA helicase B (HDHB) have suggested that its activity is critical for the G1/S transition of the cell cycle, but the nature of its role remains unknown. In this study, we show that during G1, ectopically expressed HDHB localizes in nuclear foci induced by DNA damaging agents and that this focal pattern requires active HDHB. During S and G2/M, HDHB localizes primarily in the cytoplasm. A carboxy-terminal domain from HDHB confers cell cycle-dependent localization, but not the focal pattern, to a reporter protein. A cluster of potential cyclin-dependent kinase phosphorylation sites in this domain was modified at the G1/S transition and maintained through G2/M of the cell cycle in vivo, coincident with nuclear export of HDHB. Serine 967 of HDHB was the major site phosphorylated in vivo and in vitro by cyclin-dependent kinases. Mutational analysis demonstrated that phosphorylation of serine 967 is crucial in regulating the subcellular localization of ectopically expressed HDHB. We propose that the helicase of HDHB operates primarily during G1 to process endogenous DNA damage before the G1/S transition, and it is largely sequestered in the cytoplasm during S/G2.
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: Jinming
authors.initials: J
authors.lastname: Gu
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Xia
authors.forename: Peijun
authors.initials: P
authors.lastname: Yan
authors.forename: Hanjian
authors.initials: H
authors.lastname: Liu
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Podust
authors.forename: Albert B
authors.initials: AB
authors.lastname: Reynolds
authors.forename: Ellen
authors.initials: E
authors.lastname: Fanning
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D042846:CDC2-CDC28 Kinases / Q000032:analysis / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology; D002453:Cell Cycle; D051357:Cyclin-Dependent Kinase 2; D004247:DNA / Q000187:drug effects; D004249:DNA Damage; D004265:DNA Helicases / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D004252:DNA Mutational Analysis; D016193:G1 Phase / Q000502:physiology; D006801:Humans; D042541:Intracellular Space / Q000276:immunology / Q000648:ultrastructure; D016685:Mitomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D012694:Serine / Q000235:genetics / Q000378:metabolism
chemical_list: D012694:Serine; D016685:Mitomycin; D004247:DNA; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D004265:DNA Helicases; D002166:Camptothecin