title: TGF-β-activated kinase 1 promotes cell cycle arrest and cell survival of X-ray irradiated HeLa cells dependent on p21 induction but independent of NF-κB, p38 MAPK and ERK phosphorylations.
abstract: Transforming growth factor-β-activated kinase 1 (TAK1) appears to play a role in inhibiting apoptotic death in response to multiple stresses. To assess the role of TAK1 in X-ray induced apoptosis and cell death, we irradiated parental and siRNA-TAK1-knockdown HeLa cells. Changes in gene expression levels with and without TAK1-knockdown were also examined after irradiation to elucidate the molecular mechanisms involved. After X-ray irradiation, cell death estimated by the colony formation assay increased in the TAK1-knockdown cells. Apoptosis induction, determined by caspase-3 cleavage, suggested that the increased radiosensitivity of the TAK1-knockdown cells could be partially explained by the induction of apoptosis. However, cell cycle analysis revealed that the percentage of irradiated cells in the G(2)/M-phase decreased, and those in the S- and SubG(1)-phases increased due to TAK1 depletion, suggesting that the loss of cell cycle checkpoint regulation may also be involved in the observed increased radiosensitivity. Interestingly, significant differences in the induction of NF-κB, p38 MAPK and ERK phosphorylation, the major downstream molecules of TAK1, were not observed in TAK1 knockdown cells compared to their parental control cells after irradiation. Instead, global gene expression analysis revealed differentially expressed genes after irradiation that bioinformatics analysis suggested are associated with cell cycle regulatory networks. In particular, CDKN1A (coding p21(WAF1)), which plays a central role in the identified network, was up-regulated in control cells but not in TAK1 knockdown cells after X-ray irradiation. Si-RNA knockdown of p21 decreased the percentage of cells in the G(2)/M phase and increased the percentage of cells in the S- and SubG(1)-phases after X-ray irradiation in a similar manner as TAK-1 knockdown. Taken together, these findings suggest that the role of TAK1 in cell death, cell cycle regulation and apoptosis after X irradiation is independent of NF-κB, p38 MAPK, and ERK phosphorylation, and dependent, in part, on p21 induction.
authors.affiliation: Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Furusawa
authors.forename: Zheng-Li
authors.initials: ZL
authors.lastname: Wei
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Sakurai
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Tabuchi
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.forename: Qing-Li
authors.initials: QL
authors.lastname: Zhao
authors.forename: Takaharu
authors.initials: T
authors.lastname: Nomura
authors.forename: Ikuo
authors.initials: I
authors.lastname: Saiki
authors.forename: Takashi
authors.initials: T
authors.lastname: Kondo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D059447:Cell Cycle Checkpoints / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D016193:G1 Phase / Q000528:radiation effects; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation / Q000528:radiation effects; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance / Q000528:radiation effects; D015398:Signal Transduction / Q000528:radiation effects; D059467:Transcriptome / Q000528:radiation effects; D014965:X-Rays / Q000009:adverse effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D050759:Cyclin-Dependent Kinase Inhibitor p21; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D034741:RNA, Small Interfering; C481053:TAB3 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases