title: Both ERK1 and ERK2 kinases promote G2/M arrest in etoposide-treated MCF7 cells by facilitating ATM activation.
abstract: The MEK-ERK pathway plays a role in DNA damage response (DDR). This has been thoroughly studied by modulating MEK activation. However, much less has been done to directly examine the contributions of ERK1 and ERK2 kinases to DDR. Etoposide induces G2/M arrest in a variety of cell lines, including MCF7 cells. DNA damage-induced G2/M arrest depends on the activation of the protein kinase ataxia-telangiectasia mutated (ATM). ATM subsequently activates CHK2 by phosphorylating CHK2 threonine 68 (T68) and CHK2 inactivates CDC25C via phosphorylation of its serine 216 (S216), resulting in G2/M arrest. To determine the contribution of ERK1 and ERK2 to etoposide-induced G2/M arrest, we individually knocked-down ERK1 and ERK2 in MCF7 cells using specific small interfering RNA (siRNA). Knockdown of either kinases significantly reduced ATM activation in response to etoposide treatment, and thereby attenuated phosphorylation of the ATM substrates, including the S139 of H2AX (gammaH2AX), p53 S15, and CHK2 T68. Consistent with these observations, knockdown of either ERK1 or ERK2 reduced etoposide-induced CDC25C S216 phosphorylation and significantly compromised etoposide-induced G2/M arrest in MCF7 cells. Taken together, we demonstrated that both ERK1 and ERK2 kinases play a role in etoposide-induced G2/M arrest by facilitating activation of the ATM pathway. These observations suggest that a cellular threshold level of ERK kinase activity is required for the proper checkpoint activation in MCF7 cells.
authors.affiliation: Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Fengxiang
authors.initials: F
authors.lastname: Wei
authors.forename: Yanyun
authors.initials: Y
authors.lastname: Xie
authors.forename: Lijian
authors.initials: L
authors.lastname: Tao
authors.forename: Damu
authors.initials: D
authors.lastname: Tang
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002455:Cell Division; D045744:Cell Line, Tumor; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology*; D016195:G2 Phase; D006657:Histones / Q000378:metabolism; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D006657:Histones; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D005047:Etoposide; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases