title: Cyclin B1 proteolysis via p38 MAPK signaling participates in G2 checkpoint elicited by arsenite.
abstract: Timely induction of cyclin B1 controls mitotic entry, whereas its proteolysis is essential for mitotic exit. By contrast, cyclin B1 transcription is repressed during G(2) arrest induced by DNA damage. The p38 mitogen-activated protein kinase is involved in the G(2) checkpoint; yet, its impact on cyclin B1 protein levels remains unclear. Here we show that untimely proteolysis of cyclin B1 following p38 activation contributes to G(2) checkpoint. Exposing early G(2) cells to arsenite impeded cyclin B1 protein accumulation, Cdk1 activation, and G(2)-to-M progression. Conversely, cyclin B1 was non-degradable in late G(2) and mitotic cells after arsenite. Cyclin B1 proteolysis was enhanced by arsenite in early G(2) and asynchronous cells. This rapid destruction of cyclin B1 was mediated via the ubiquitin-proteasome pathway probably in a Cdc20 and Cdh1 independent mechanism. Under arsenite, inhibition of p38 activation or depletion of p38alpha suppressed cyclin B1 ubiquitination and proteolysis, while forced expression of MKK6-p38 accelerated these events. Inactivation of p38 in arsenite-treated early G(2) cells allowed G(2)-to-M progression, blocked apoptosis, increased cell viability, and decreased micronucleus formation. Thus, p38 signaling pathway triggering cyclin B1 proteolysis after arsenite may play an important role in connecting G(2) arrest with apoptosis or genome instability.
authors: Molecular Carcinogenesis Laboratory, Institute of Biotechnology and Department of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan.
authors: Ju-Pi
authors: JP
authors: Li
authors: Jia-Ling
authors: JL
authors: Yang
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D017209:Apoptosis / Q000187:drug effects; D018053:Arsenites / Q000633:toxicity*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002274:Carcinogens, Environmental / Q000633:toxicity*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019926:Cyclin B / Q000378:metabolism*; D056744:Cyclin B1; D003513:Cycloheximide / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects; D048308:Mitogen-Activated Protein Kinase 14 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects*; D010447:Peptide Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D011480:Protease Inhibitors; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D017670:Sodium Compounds / Q000633:toxicity*; D025801:Ubiquitin / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism
chemical_list: D018053:Arsenites; C534699:CCNB1 protein, human; D002274:Carcinogens, Environmental; D019926:Cyclin B; D056744:Cyclin B1; D007093:Imidazoles; D007976:Leupeptins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D047428:Protein Kinase Inhibitors; D011500:Protein Synthesis Inhibitors; D011725:Pyridines; D017670:Sodium Compounds; D025801:Ubiquitin; C017947:sodium arsenite; D003513:Cycloheximide; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D016203:CDC2 Protein Kinase; D048308:Mitogen-Activated Protein Kinase 14; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde