title: An essential role for MCL-1 in ATR-mediated CHK1 phosphorylation.
abstract: Here we report a novel role for myeloid cell leukemia 1 (Mcl-1), a Bcl-2 family member, in regulating phosphorylation and activation of DNA damage checkpoint kinase, Chk1. Increased expression of nuclear Mcl-1 and/or a previously reported short nuclear form of Mcl-1, snMcl-1, was observed in response to treatment with low concentrations of etoposide or low doses of UV irradiation. We showed that after etoposide treatment, Mcl-1 could coimmunoprecipitate with the regulatory kinase, Chk1. Chk1 is a known regulator of DNA damage response, and its phosphorylation is associated with activation of the kinase. Transient transfection with Mcl-1 resulted in an increase in the expression of phospho-Ser345 Chk1, in the absence of any evidence of DNA damage, and accumulation of cells in G2. Importantly, knockdown of Mcl-1 expression abolished Chk1 phosphorylation in response to DNA damage. Mcl-1 could induce Chk1 phosphorylation in ATM-negative (ataxia telangectasia mutated) cells, but this response was lost in ATR (AT mutated and Rad3 related)-defective cells. Low levels of UV treatment also caused transient increases in Mcl-1 levels and an ATR-dependent phosphorylation of Chk1. Together, our results strongly support an essential regulatory role for Mcl-1, perhaps acting as an adaptor protein, in controlling the ATR-mediated regulation of Chk1 phosphorylation.
authors.affiliation: Department of Medicine, University of British Columbia and Vancouver Coastal Health Research Institute, Vancouver, BC, V6H 3Z6 Canada.
authors.forename: Sarwat
authors.initials: S
authors.lastname: Jamil
authors.forename: Shadi
authors.initials: S
authors.lastname: Mojtabavi
authors.forename: Payman
authors.initials: P
authors.lastname: Hojabrpour
authors.forename: Stefanie
authors.initials: S
authors.lastname: Cheah
authors.forename: Vincent
authors.initials: V
authors.lastname: Duronio
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D004249:DNA Damage; D005047:Etoposide / Q000494:pharmacology; D005786:Gene Expression Regulation; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D018797:Cell Cycle Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D005047:Etoposide; D011494:Protein Kinases; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases