Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 280, Issue 17, Pages 16821-16828Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M413753200
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Funding
- NCI NIH HHS [CA27607] Funding Source: Medline
- NIAID NIH HHS [AI45150] Funding Source: Medline
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TFII-I is a signal-induced multi-functional transcription factor that has recently been implicated as a regulatory component of the endoplasmic reticulum ( ER) stress response. TFII-I acts through ER stress-induced binding to the ER stress element, which is highly conserved in promoters of ER stress-inducible genes such as Grp78/BiP. Interestingly, its tyrosine phosphorylation sites are required for its activation of the Grp78 promoter. Toward understanding the link between TFII-I, the tyrosine kinase signaling pathway, and Grp78 activation, we discovered that Tg stress induces a dramatic increase of TFII-I phosphorylation at Tyr(248) and localization of this form of TFII-I to the nucleus. Chromatin immunoprecipitation analysis further reveals enhanced TFII-I binding to the Grp78 promoter in vivo upon ER stress. Previously, we reported that genistein, a general inhibitor of tyrosine kinase, could suppress ER stress induction of Grp78 by inhibiting complex formation on the ER stress element; however, the mechanism is not known. Consistent with TFII-I being a target of genistein suppression, we observed that genistein could suppress Tg stress-induced phosphorylation of TFII-I. We further demonstrate that c-Src, which is one of kinases identified to mediate phosphorylation of TFII-I at Tyr(248), is activated by Tg stress and is able to stimulate the Grp78 promoter activity. Lastly, using stable cell lines with suppressed TFII-I levels, we show that TFII-I is required for optimal induction of Grp78 by ER stress. Our studies provide a molecular link that connects the c-Src tyrosine kinase transduction pathway to ER stress-induced transcriptional activation of Grp78 mediated by TFII- I.
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