Transcriptional Regulation of the Grp78 Promoter by Endoplasmic Reticulum Stress

Abstract

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 Tyr248 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 Tyr248, 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. 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 Tyr248 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 Tyr248, 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. When mammalian cells are subjected to a variety of physiological stress conditions that target the endoplasmic reticulum (ER), 1The abbreviations used are: ER, endoplasmic reticulum; Bsd, blasticidin; CAT, chloramphenicol acetyltransferase; ERSE, ER stress response element; MMTV, mouse mammary tumor virus; Tg, thapsigargin; Tuni, Tunicamycin; UPR, unfolded protein response; GST, glutathione S-transferase; AS, antisense vector; V, empty vector. the cells respond by activating a defense mechanism referred to as the unfolded protein response (UPR), a mechanism evolutionarily conserved from yeast to human (1Foti D.M. Welihinda A. Kaufman R.J. Lee A.S. J. Biol. Chem. 1999; 274: 30402-30409Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar, 2Kaufman R.J. J. Clin. Invest. 2002; 110: 1389-1398Crossref PubMed Scopus (1098) Google Scholar). For example, when mammalian cells are treated with thapsigargin (Tg), which blocks the ER calcium ATPase pump, thereby depleting the ER calcium store, the UPR is triggered, resulting in translational arrest, induction of cell death pathways, and transcriptional activation of cellular genes that promote survival. A major cellular target of the UPR is GRP78/BiP, an ER chaperone with anti-apoptotic properties (3Reddy R.K. Mao C. Baumeister P. Austin R.C. Kaufman R.J. Lee A.S. J. Biol. Chem. 2003; 278: 20915-20924Abstract Full Text Full Text PDF PubMed Scopus (626) Google Scholar). GRP78 not only binds to unfolded proteins but also regulates the activation of ER stress signal transducers (4Bertolotti A. Zhang Y. Hendershot L.M. Harding H.P. Ron D. Nat. Cell Biol. 2000; 2: 326-332Crossref PubMed Scopus (2104) Google Scholar, 5Lee A.S. Trends Biochem. Sci. 2001; 26: 504-510Abstract Full Text Full Text PDF PubMed Scopus (921) Google Scholar, 6Shen J. Chen X. Hendershot L. Prywes R. Dev. Cell. 2002; 3: 99-111Abstract Full Text Full Text PDF PubMed Scopus (1074) Google Scholar). Because the induction of GRP78 is regulated primarily at the transcriptional level, activation of the Grp78 promoter is used extensively as a biological marker for the onset of ER stress and the UPR. GRP78 belongs to a family of proteins referred to as the glucose-regulated proteins (5Lee A.S. Trends Biochem. Sci. 2001; 26: 504-510Abstract Full Text Full Text PDF PubMed Scopus (921) Google Scholar, 7Lee A.S. Trends Biochem. Sci. 1987; 12: 20-23Abstract Full Text PDF Scopus (393) Google Scholar, 8Little E. Ramakrishnan M. Roy B. Gazit G. Lee A.S. Crit. Rev. Eukaryotic Gene Expression. 1994; 4: 1-18Crossref PubMed Scopus (357) Google Scholar). The Grp promoters contain multiple copies of the ER stress response element (ERSE), which consists of a unique tripartite structure CCAAT(N9)CCACG (9Yoshida H. Haze K. Yanagi H. Yura T. Mori K. J. Biol. Chem. 1998; 273: 33741-33749Abstract Full Text Full Text PDF PubMed Scopus (1018) Google Scholar, 10Roy B. Lee A.S. Nucleic Acids Res. 1999; 27: 1437-1443Crossref PubMed Scopus (216) Google Scholar). Within a subset of mammalian ERSEs, N9 represents a GC-rich sequence of 9 bp that is conserved across species. Previously, we observed that a protein complex exhibits enhanced binding to the ERSE of Grp promoters following Tg stress and that optimal binding of this complex to the ERSE and maximal ERSE-mediated stress inducibility require the conserved GGC motif within the 9-bp region (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). This complex is different from the NF-Y/CBF and ATF6·YY1 complexes that interact with the CCAAT and CCACG elements, respectively (10Roy B. Lee A.S. Nucleic Acids Res. 1999; 27: 1437-1443Crossref PubMed Scopus (216) Google Scholar, 12Yoshida H. Okada T. Haze K. Yanagi H. Yura T. Negishi M. Mori K. Mol. Cell. Biol. 2001; 21: 1239-1248Crossref PubMed Scopus (260) Google Scholar, 13Li W.W. Hsiung Y. Zhou Y. Roy B. Lee A.S. Mol. Cell. Biol. 1997; 17: 54-60Crossref PubMed Scopus (82) Google Scholar). Subsequently, the protein binding to the GGC motif within the ERSE has been identified as the multifunctional transcription factor TFII-I (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). Further, TFII-I stimulates the activity of ATF6, which is specifically processed and activated upon ER stress (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar, 12Yoshida H. Okada T. Haze K. Yanagi H. Yura T. Negishi M. Mori K. Mol. Cell. Biol. 2001; 21: 1239-1248Crossref PubMed Scopus (260) Google Scholar). Although TFII-I was originally discovered as a basal factor required for initiator-dependent transcription in vitro, it can also bind specifically to both upstream activator sites and core promoter elements through distinct DNA-binding domains (14Roy A.L. Gene (Amst.). 2001; 274: 1-13Crossref PubMed Scopus (93) Google Scholar). TFII-I exists as multiple alternatively spliced isoforms ranging in size from 120 to 150 kDa. A distinct feature of TFII-I and its related protein family members is that it contains six directly repeated 90-residue motifs that each possesses a potential helix-loop/span-helix homology. These unique structural features that TFII-I the for multiple and the formation of activator complexes and a link with the basal transcription TFII-I also a in signal TFII-I is at and tyrosine and its activity is regulated by phosphorylation Cheriyath V. Roy A.L. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). Interestingly, ER stress induction of Grp78 can suppressed by genistein, a tyrosine kinase inhibitor Y. Lee A.S. J. 1998; PubMed Scopus Google Scholar). genistein the formation of complexes on the ERSE is also that in to the ER stress signaling a pathway mediated by tyrosine kinase could also kinase that regulates tyrosine phosphorylation and transcriptional activity of TFII-I is has been reported that TFII-I a tyrosine kinase phosphorylation on tyrosine Tyr248 and and to the in response to factor signaling V. Roy A.L. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). has also been reported that which is a target of activation TFII-I, is required for Tg stress induction of however, the mechanism is not H. K. 2000; PubMed Scopus Google Scholar). Toward understanding signal transduction that ER stress induction of the Grp78 we provide that TFII-I could a target of genistein We demonstrate that Tg stress induces TFII-I phosphorylation at Tyr248, with its localization and enhanced to the Grp78 promoter in We further a between Tg stress-induced c-Src activation and TFII-I to Grp78 Lastly, using stable cell lines with suppressed TFII-I level, we show that TFII-I is required in vivo for optimal induction of Grp78 by ER stress. Our studies provide a link that connects the tyrosine kinase transduction pathway to a transcriptional activation mechanism for Grp78 induction in response to ER stress. Cell and cells in and at For stress the cells to and treated with Tg genistein for the referred to as T. L. Lee A.S. Sci. A. 1987; PubMed Scopus Google contains the Grp78 promoter with the the of chloramphenicol The contains copies of to the promoter of mouse mammary tumor the of W.W. X. Lee A.S. J. Biol. Chem. Full Text PDF PubMed Google Scholar). contains the promoter to the Lee A.S. Gene (Amst.). PubMed Scopus Google Scholar). The of for the has been V. Roy A.L. Mol. Cell. Biol. 1998; PubMed Google Scholar). The of the tyrosine phosphorylation of TFII-I referred to as the has been Cheriyath V. Roy A.L. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). The antisense for TFII-I, referred to as is from the and has been (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). The which from to of the Grp78 promoter with ERSEs, has been Lee A.S. Biochem. J. 2002; PubMed Google Scholar). The the c-Src has been V. Roy A.L. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). of Cell cells conditions and using with the and empty the a of the sequence on the TFII-I in an antisense (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). the cells in a and in the of of for at and protein from the cell lines referred to as cells from the cell lines referred to as cells and for TFII-I protein by for cellular and been X. Zhou Y. Lee A.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The used for the of Grp78 and also been Y. Lee A.S. J. 1998; PubMed Scopus Google Scholar). and of Gene the cells in and to of the was with of an for the of the promoter that was used as an for For stress the cells treated with Tg, genistein Tg with genistein for to of the cell for and the of the been W.W. X. Lee A.S. J. Biol. Chem. Full Text PDF PubMed Google Scholar). Cell to For the cells cells to of the was with of in using The of in each was to the by of the empty in the The cells in conditions subjected to Tg the cell for using a was in and repeated for analysis of GRP78 and with the mouse been (3Reddy R.K. Mao C. Baumeister P. Austin R.C. Kaufman R.J. Lee A.S. J. Biol. Chem. 2003; 278: 20915-20924Abstract Full Text Full Text PDF PubMed Scopus (626) Google Scholar). for analysis of TFII-I and been (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). For of an from of was used as the at a of The used was at a of For of c-Src, the was used as the at a of The used was at a of For of c-Src, the mouse was used as the at a of The used was at a of of the protein was with an cells with TFII-I cells in cell 150 with the of one inhibitor of The cell by at for at For of cell with protein and of the the with The was subjected to with and the was subjected to with Chromatin cells in cell conditions to and treated with Tg for The conditions for immunoprecipitation been Lee A.S. Biochem. J. 2002; PubMed Google Scholar). of from each at with of of The used for the Grp78 promoter and a cells on the cells in for of the cells with Tg for the cells with and with as the a of with the cells with with for The cells with and with to the and on and using the was used for of TFII-I ER Grp the of ER TFII-I induction at the protein level, we the cell the basal TFII-I is with cell Tg was a increase in the TFII-I protein Consistent with TFII-I being a transcription activator for the of increase in TFII-I protein following Tg the increase in GRP78 and This was also observed when the cells treated with TFII-I with the Grp78 promoter in immunoprecipitation with cells subjected to Tg the as the and of we TFII-I binding to the Grp78 promoter in upon of Tg was a increase in TFII-I binding core binding to the promoter region was and Tg These that in this cell an increase in TFII-I can in Grp78 This was when cells with and an for TFII-I, and an increase in activity was observed in a with TFII-I TFII-I a of ER by of the unique structural domains of TFII-I with the of the tyrosine Tyr248 and is in that the tyrosine phosphorylation at Tyr248 and are for its activity on the Grp78 cells with and TFII-I in which the tyrosine are to The TFII-I was able to stimulate the This is with the that the at Tyr248 and are not required for the TFII-I to bind to are for its activity Cheriyath V. Roy A.L. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). ER stress the of TFII-I tyrosine phosphorylation and this is on the at Tyr248 and cells with TFII-I The cells treated with Tg, genistein, a of the The protein subjected to immunoprecipitation with by with We observed a basal of tyrosine phosphorylation of TFII-I in cells and this was enhanced by following Tg and of cells with the tyrosine kinase genistein, the basal of tyrosine phosphorylation of TFII-I by genistein TFII-I tyrosine phosphorylation enhanced phosphorylation of was observed following Tg that Tg stress-induced tyrosine phosphorylation of TFII-I primarily on the tyrosine at Tyr248 and and that this can suppressed by ER of the Grp78 through the that genistein has on the basal of Grp78 but can suppress Grp78 induction by Y. Lee A.S. J. 1998; PubMed Scopus Google we observed that genistein can also the activation of Grp78 by Tg and not genistein is a general inhibitor of ER stress the mechanism of such by genistein is mediated through the ERSE of the Grp78 was of we discovered that genistein, an ATPase the activity of not genes in are which contains bp of the Grp78 promoter the which contains copies of the upstream of the promoter the element; and the empty The cells treated with Tg, genistein, We observed that genistein not the basal promoter activity of of the but was able to suppress Tg induction in that the ERSE to its as in the of a as in the of These are with a genistein target being a transcription factor such as TFII-I that binds and acts through the ERSE of the Grp78 promoter. ER of and Tyr248 of TFII-I has been to for Grp78 activation, we to Tg stress induces phosphorylation specifically at this for TFII-I was with cells treated with A TFII-I at Tyr248 was used V. Roy A.L. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). We observed that in the was and in the Tg was enhanced and in the nucleus. Tg of c-Src and TFII-I of the Grp78 TFII-I is at Tyr248 in a upon by V. Roy A.L. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). Tg stress activation, cells with c-Src and the of tyrosine phosphorylation of c-Src following Tg conditions by the was a of c-Src, and the of tyrosine phosphorylation was the the cells with the c-Src an increase in c-Src protein Tg an increase in phosphorylation of c-Src was observed at of and this increase was to 120 the of with the Tg stress-induced phosphorylation of TFII-I at Tyr248 of c-Src can in Grp78 of the c-Src with We observed that c-Src could the Grp78 promoter activity in a in the of ER stress the a induction was as with the induction by Tg Consistent with c-Src to Tg induction of the Grp78 of c-Src Tg stress induction of the Grp78 promoter activity and the of Grp78 by c-Src is mediated through TFII-I, the cells with the with TFII-I and c-Src We observed that c-Src and TFII-I the Grp78 and in was a further and The an mechanism between the c-Src and TFII-I in the that TFII-I is a target for c-Src of the form of c-Src of TFII-I mediated of the Grp78 promoter at the it on the activity and TFII-I a transcription for ER of directly TFII-I is required for ER stress induction of we stable cell lines that TFII-I of the of the cells with the antisense for TFII-I the empty with a for with to the the cells and for The cell lines the TFII-I antisense and the empty are as the and Because the ERSE of the Grp78 promoter is regulated by a of transcription ATF6, and the and the cell lines provide a to TFII-I is required for ER stress induction of its target genes in We observed that the basal of Grp78 in the cell is that of cell and that the induction of Grp78 by Tg and was by in the cell as with the cell This that TFII-I is required in vivo for optimal induction of Grp78 by ER stress. the of induction of GRP78 at the protein in the and cell cell from cells treated with Tg for and was to the of GRP78 as as an ER molecular chaperone that is regulated with GRP78 A.S. Trends Biochem. Sci. 1987; 12: 20-23Abstract Full Text PDF Scopus (393) Google Scholar, Lee A.S. Mol. Cell. Biol. PubMed Scopus Google Scholar). the was for the of TFII-I and in the induction of both GRP78 and protein by Tg was suppressed in the cell which a TFII-I The transcriptional of ER by ER stress as by GRP78 induction is an pathway ER stress can the UPR, which can on cell death as as The between has in and (5Lee A.S. Trends Biochem. Sci. 2001; 26: 504-510Abstract Full Text Full Text PDF PubMed Scopus (921) Google Scholar, Zhou J. Austin R.C. J. Clin. Invest. 2001; PubMed Scopus Google Scholar, X. B. J. PubMed Scopus Google Scholar, D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). studies on the transcription activation of Grp78 on the transcription such as ATF6, and that interact with the ERSE (10Roy B. Lee A.S. Nucleic Acids Res. 1999; 27: 1437-1443Crossref PubMed Scopus (216) Google Scholar, 13Li W.W. Hsiung Y. Zhou Y. Roy B. Lee A.S. Mol. Cell. Biol. 1997; 17: 54-60Crossref PubMed Scopus (82) Google Scholar, Lee A.S. Biochem. J. 2002; PubMed Google Scholar, M. Baumeister P. Roy B. Phan T. D. Lee A.S. Mol. Cell. Biol. 2000; PubMed Scopus Google Scholar, H. T. A. Okada T. Mori K. Cell. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Baumeister P. R.K. M. Lee A.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Although that elements the ERSE can also Grp78 promoter activity in response to ER of the Grp78 promoter that the ERSE is the regulatory element for the ER transcription activation of the Grp78 promoter (9Yoshida H. Haze K. Yanagi H. Yura T. Mori K. J. Biol. Chem. 1998; 273: 33741-33749Abstract Full Text Full Text PDF PubMed Scopus (1018) Google Scholar, Baumeister P. Lee A.S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). and we identified TFII-I as a activator of the ERSE through binding to the GC-rich sequence motif of the ERSE (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). Interestingly, the of TFII-I and protein in response to a variety of ER TFII-I the of a transcription factor that regulates UPR target genes and is by the UPR at the we further the mechanism of Tg stress-induced TFII-I activation of the Grp78 promoter. These studies Tg stress-induced activation of c-Src and enhanced tyrosine phosphorylation of TFII-I at Tyr248, as as Tg stress-induced localization of this form of TFII-I and enhanced binding of TFII-I to the Grp78 promoter in vivo resulting in promoter activation Our are with that conditions and using an that can between different TFII-I TFII-I is and the upon tyrosine phosphorylation V. Roy A.L. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar, Cheriyath V. Zhang K. Roy A.L. Mol. Cell. Biol. 1999; PubMed Scopus Google Scholar). We further the of TFII-I in induction by stable cell lines that antisense TFII-I. the of TFII-I was and the TFII-I ER stress. cells and cells with the empty we demonstrate that TFII-I is required for optimal induction of GRP78 by members of the This is by the that a major ER chaperone that is with GRP78 at the transcription level, is also on TFII-I for induction following ER stress Lee A.S. Mol. Cell. Biol. PubMed Scopus Google Scholar). Further, the of TFII-I is not to ER calcium stress such as of protein as as of also require TFII-I to the The that TFII-I is a transcription factor for Grp induction the as to it is for optimal Grp promoter we discovered that TFII-I is a for (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). Although is able to bind the ERSE, it the of in the H. T. A. Okada T. Mori K. Cell. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). one mechanism is that TFII-I, through its unique structure of can binding to the ERSE, in with binding such as and Consistent with this is the that optimal activation of the ERSE is on TFII-I (11Parker R. Phan T. Baumeister P. Roy B. Cheriyath V. Roy A.L. Lee A.S. Mol. Cell. Biol. 2001; 21: 3220-3233Crossref PubMed Scopus (91) Google Scholar). TFII-I also the of upstream activating complexes to the basal transcription (14Roy A.L. Gene (Amst.). 2001; 274: 1-13Crossref PubMed Scopus (93) Google Scholar). the of TFII-I in complex formation and to the basal promoter core elements could in the of TFII-I in cells ER stress induction of Grp78 for TFII-I a ER stress-induced tyrosine kinase signaling pathway to the induction of ER chaperone The of a tyrosine kinase pathway in the ER stress response was discovered through the that genistein, a tyrosine kinase can the increase of Grp78 transcription by Tg and that this is mediated through the ERSE X. Zhou Y. Lee A.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The of genistein is general it also induction by as as was further that of cells with genistein in the of transcription factor binding to the ERSE Y. Lee A.S. J. 1998; PubMed Scopus Google Scholar). genistein the ER stress response is not we that TFII-I could one target for the of genistein on the following in this TFII-I dramatic increase in tyrosine phosphorylation ER stress. The phosphorylation the at tyrosine at Tyr248 and the ER increase in phosphorylation is when are Further, through the of Tyr248, we a dramatic increase in TFII-I phosphorylation at this and localization upon ER stress. it has been that are required for the transcription of TFII-I Cheriyath V. Roy A.L. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). we that of in a of the transcriptional activity of TFII-I on the Grp78 promoter. we that genistein could the ER stress-induced tyrosine phosphorylation of TFII-I. that the tyrosine phosphorylation at the Tyr248 and is not required for the binding of TFII-I Cheriyath V. Roy A.L. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). one mechanism is that the phosphorylation of TFII-I at its to complex with thereby with its to the Grp complex and its activating of c-Src as a potential kinase tyrosine phosphorylation of TFII-I on Tyr248 V. Roy A.L. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google we that c-Src is activated by Tg stress. of c-Src can the Grp78 the of c-Src can suppress Tg stress as as activation of the Grp78 promoter. The of on TFII-I mediated activation of the Grp78 promoter that TFII-I is a potential target of c-Src, kinase able to for c-Src in activating TFII-I Mol. Cell. Biol. 2000; PubMed Scopus Google Scholar). Our also a mechanism for the of in the Tg stress induction of the Grp78 promoter mediated by the ERSE (5Lee A.S. Trends Biochem. Sci. 2001; 26: 504-510Abstract Full Text Full Text PDF PubMed Scopus (921) Google Scholar, H. K. 2000; PubMed Scopus Google Scholar). is that the being a target of the tyrosine form of TFII-I V. Roy A.L. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google is activated by Tg stress. This to an increase in protein as by analysis H. K. 2000; PubMed Scopus Google through complex formation with the Grp78 transcriptional to Tg stress-induced activation of the Grp78 promoter. that TFII-I as a of ER stress on multiple in cell lines with basal TFII-I ER stress the of TFII-I to transcriptional activation of its target genes such as Grp78 and ER stress the phosphorylation of TFII-I. Within of ER is a increase in tyrosine phosphorylation of TFII-I and an increase in binding to the Grp78 promoter in vivo as by immunoprecipitation These unique properties of TFII-I that not only can it as a transcriptional activator in a of promoter complex and of it can also provide a molecular link between the activation of a tyrosine kinase pathway and the UPR. studies the of the tyrosine kinase could provide the onset of the UPR. We for the