title: Regulation of late G1/S phase transition and APC Cdh1 by reactive oxygen species.
abstract: Proliferating cells have a higher metabolic rate than quiescent cells. To investigate the role of metabolism in cell cycle progression, we examined cell size, mitochondrial mass, and reactive oxygen species (ROS) levels in highly synchronized cell populations progressing from early G1 to S phase. We found that ROS steadily increased, compared to cell size and mitochondrial mass, through the cell cycle. Since ROS has been shown to influence cell proliferation and transformation, we hypothesized that ROS could contribute to cell cycle progression. Antioxidant treatment of cells induced a late-G1-phase cell cycle arrest characterized by continued cellular growth, active cyclin D-Cdk4/6 and active cyclin E-Cdk2 kinases, and inactive hyperphosphorylated pRb. However, antioxidant-treated cells failed to accumulate cyclin A protein, a requisite step for initiation of DNA synthesis. Further examination revealed that cyclin A continued to be ubiquitinated by the anaphase promoting complex (APC) and to be degraded by the proteasome. This antioxidant arrest could be rescued by overexpression of Emi1, an APC inhibitor. These observations reveal an intrinsic late-G1-phase checkpoint, after transition across the growth factor-dependent G1 restriction point, that links increased steady-state levels of endogenous ROS and cell cycle progression through continued activity of APC in association with Cdh1.
authors.affiliation: Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, University of California-San Diego, School of Medicine, 9500 Gilman Dr., La Jolla, CA 92093-0686, USA.
authors.forename: Courtney G
authors.initials: CG
authors.lastname: Havens
authors.forename: Alan
authors.initials: A
authors.lastname: Ho
authors.forename: Naohisa
authors.initials: N
authors.lastname: Yoshioka
authors.forename: Steven F
authors.initials: SF
authors.lastname: Dowdy
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001483:Base Sequence; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000235:genetics; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D008954:Models, Biological; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism; D016196:S Phase / Q000187:drug effects / Q000502:physiology; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D018797:Cell Cycle Proteins; D019925:Cyclin A; D044783:F-Box Proteins; C498960:FBXO5 protein, human; D017382:Reactive Oxygen Species; D016160:Retinoblastoma Protein; D004247:DNA; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome