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A reinvestigation of the multisite phosphorylation of the transcription factor c‐Jun
Author(s) -
Morton Simon,
Davis Roger J.,
McLaren Ann,
Cohen Philip
Publication year - 2003
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdg388
Subject(s) - dephosphorylation , phosphorylation , anisomycin , biology , kinase , phosphatase , phosphorylation cascade , protein phosphorylation , microbiology and biotechnology , protein kinase c , protein kinase a , biochemistry
We have used phospho‐specific antibodies to re‐examine the multisite phosphorylation of c‐Jun in murine RAW macrophages and embryonic fibroblasts. Our results indicate that JNK isoforms are required and sufficient for the phosphorylation of Thr91 and Thr93, as well as the phosphorylation of Ser63 and Ser73, in response to LPS or anisomycin in macrophages and TNFα or anisomycin in fibroblasts. However, the phorbol ester (TPA) and EGF‐induced phosphorylation of Ser63 and Ser73 is mediated by ERK1/ERK2, as well as JNK1/JNK2, in fibroblasts from wild‐type mice and by ERK1/ERK2 alone in fibroblasts from JNK‐deficient mice. The phosphorylation of Thr239 is catalysed by GSK3 and the phosphorylation of Ser243 by an as yet unidentified protein kinase. The inhibition of GSK3 is not required for the dephosphorylation of Thr239 in response to LPS, and nor is the phosphorylation of Thr91 and Thr93 required for the TPA‐ or EGF‐induced dephosphorylation of Thr239 in fibroblasts. The agonist‐induced dephosphorylation of Thr239 may involve a conformational change that exposes Thr239 to dephosphorylation and/or the activation of a Thr239 phosphatase.