title: Elevated cyclin G2 expression intersects with DNA damage checkpoint signaling and is required for a potent G2/M checkpoint arrest response to doxorubicin.
abstract: To maintain genomic integrity DNA damage response (DDR), signaling pathways have evolved that restrict cellular replication and allow time for DNA repair. CCNG2 encodes an unconventional cyclin homolog, cyclin G2 (CycG2), linked to growth inhibition. Its expression is repressed by mitogens but up-regulated during cell cycle arrest responses to anti-proliferative signals. Here we investigate the potential link between elevated CycG2 expression and DDR signaling pathways. Expanding our previous finding that CycG2 overexpression induces a p53-dependent G(1)/S phase cell cycle arrest in HCT116 cells, we now demonstrate that this arrest response also requires the DDR checkpoint protein kinase Chk2. In accord with this finding we establish that ectopic CycG2 expression increases phosphorylation of Chk2 on threonine 68. We show that DNA double strand break-inducing chemotherapeutics stimulate CycG2 expression and correlate its up-regulation with checkpoint-induced cell cycle arrest and phospho-modification of proteins in the ataxia telangiectasia mutated (ATM) and ATM and Rad3-related (ATR) signaling pathways. Using pharmacological inhibitors and ATM-deficient cell lines, we delineate the DDR kinase pathway promoting CycG2 up-regulation in response to doxorubicin. Importantly, RNAi-mediated blunting of CycG2 attenuates doxorubicin-induced cell cycle checkpoint responses in multiple cell lines. Employing stable clones, we test the effect that CycG2 depletion has on DDR proteins and signals that enforce cell cycle checkpoint arrest. Our results suggest that CycG2 contributes to DNA damage-induced G(2)/M checkpoint by enforcing checkpoint inhibition of CycB1-Cdc2 complexes.
authors.affiliation: Department of Pharmacology, University of California, Davis, California 95616, USA.
authors.forename: Maike
authors.initials: M
authors.lastname: Zimmermann
authors.forename: Aruni S
authors.initials: AS
authors.lastname: Arachchige-Don
authors.forename: Michaela S
authors.initials: MS
authors.lastname: Donaldson
authors.forename: Robert F
authors.initials: RF
authors.lastname: Dallapiazza
authors.forename: Colleen E
authors.initials: CE
authors.lastname: Cowan
authors.forename: Mary C
authors.initials: MC
authors.lastname: Horne
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D064447:Checkpoint Kinase 2; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1 / Q000378:metabolism; D056767:Cyclin G2 / Q000235:genetics* / Q000378:metabolism; D018844:Cyclin-Dependent Kinases; D004249:DNA Damage / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects / Q000502:physiology*; D018816:Genes, cdc / Q000187:drug effects / Q000502:physiology; D045325:HCT116 Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D015689:Oncogene Protein p21(ras) / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; C534699:CCNB1 protein, human; C101593:CCNG2 protein, human; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D056767:Cyclin G2; D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D004317:Doxorubicin; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; C578634:CHEK2 protein, human; C578633:Chek2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; D018844:Cyclin-Dependent Kinases; D015689:Oncogene Protein p21(ras)