title: c-Abl-mediated tyrosine phosphorylation of JunB is required for Adriamycin-induced expression of p21.
abstract: The non-receptor-type tyrosine kinase c-Abl functions as a cytoplasmic signal transducer upon activation of cell-surface receptors. c-Abl is also involved in DDR (DNA-damage response), which is initiated in the nucleus, whereas its molecular functions in DDR are not fully understood. In the present study, we found that c-Abl phosphorylates JunB, a member of the AP-1 (activator protein 1) transcription factor family. Because JunB was suggested to be involved in DDR, we analysed the role of c-Abl-mediated phosphorylation of JunB in DDR. We first analysed phosphorylation sites of JunB and found that c-Abl majorly phosphorylates JunB at Tyr(173), Tyr(182) and Tyr(188). Because c-Abl promotes expression of the cyclin-dependent kinase inhibitor p21 upon stimulation with the DNA-damaging agent Adriamycin (doxorubicin), we analysed the involvement of JunB in Adriamycin-induced p21 expression. We found that JunB suppresses p21 induction through inhibition of its promoter activity. The phosphomimetic JunB, which was generated by glutamic acid substitutions at the phosphorylation sites, failed to repress p21 induction. Recruitment of JunB to the p21 promoter was promoted by Adriamycin stimulation and was further enhanced by co-treatment with the c-Abl inhibitor imatinib. The phosphomimetic glutamic acid substitutions in JunB or Adriamycin treatment impaired the JunB-c-Fos transcription factor complex formation. Taken together, these results suggest that, although JunB represses p21 promoter activity, c-Abl phosphorylates JunB and conversely inhibits its suppressive role on p21 promoter activity upon Adriamycin stimulation. Therefore JunB is likely to be a key target of c-Abl in expression of p21 in Adriamycin-induced DDR.
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan yamaguchinoritaka@chiba-u.jp nyama@faculty.chiba-u.jp.
authors.forename: Noritaka
authors.initials: N
authors.lastname: Yamaguchi
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan.
authors.forename: Ryuzaburo
authors.initials: R
authors.lastname: Yuki
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Kubota
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Aoyama
authors.affiliation: Laboratory of Proteome Research, National Institute of Biomedical Innovation, Ibaraki, Osaka 567-0085, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Kuga
authors.affiliation: Laboratory of Proteome Research, National Institute of Biomedical Innovation, Ibaraki, Osaka 567-0085, Japan.
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Hashimoto
authors.affiliation: Laboratory of Proteome Research, National Institute of Biomedical Innovation, Ibaraki, Osaka 567-0085, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tomonaga
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan yamaguchinoritaka@chiba-u.jp nyama@faculty.chiba-u.jp.
authors.forename: Naoto
authors.initials: N
authors.lastname: Yamaguchi
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000235:genetics; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D016315:Proto-Oncogene Proteins c-abl / Q000235:genetics / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000903:Antibiotics, Antineoplastic; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C581727:JunB protein, human; D016760:Proto-Oncogene Proteins c-fos; D014157:Transcription Factors; D004317:Doxorubicin; D016315:Proto-Oncogene Proteins c-abl
keywords: AP1 transcription factor; Adriamycin; DNA-damage response; JunB; c-Abl; cyclin-dependent kinase inhibitor; p21; p53