Identification of TFII-I as the endoplasmic reticulum stress response element binding factor ERSF: its autoregulation by stress and interaction with ATF6.
When mammalian cells are subjected to stress targeted to the endoplasmic reticulum (ER), such as depletion of the ER Ca(2+) store, the transcription of a family of glucose-regulated protein (GRP) genes encoding ER chaperones is induced. The GRP promoters contain multiple copies of the ER stress response element (ERSE), consisting of a unique tripartite structure, CCAAT(N(9))CCACG. Within a subset of mammalian ERSEs, N(9) represents a GC-rich sequence of 9 bp that is conserved across species. A novel complex (termed ERSF) exhibits enhanced binding to the ERSE of the grp78 and ERp72 promoters using HeLa nuclear extracts prepared from ER-stressed cells. Optimal binding of ERSF to ERSE and maximal ERSE-mediated stress inducibility require the conserved GGC motif within the 9-bp region. Through chromatographic purification and subsequent microsequencing, we have identified ERSF as TFII-I. Whereas TFII-I remains predominantly nuclear in both nontreated NIH 3T3 cells and cells treated with thapsigargin (Tg), a potent inducer of the GRP stress response through depletion of the ER Ca(2+) store, the level of TFII-I transcript was elevated in Tg-stressed cells, correlating with an increase in TFII-I protein level in the nuclei of Tg-stressed cells. Purified recombinant TFII-I isoforms bind directly to the ERSEs of grp78 and ERp72 promoters. The stimulation of ERSE-mediated transcription by TFII-I requires the consensus tyrosine phosphorylation site of TFII-I and the GGC sequence motif of the ERSE. We further discovered that TFII-I is an interactive protein partner of ATF6 and that optimal stimulation of ERSE by ATF6 requires TFII-I.
Parker
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R
Department of Biochemistry and Molecular Biology and the USC/Norris Comprehensive Cancer Center, Keck School of Medicine of the University of Southern California, Los Angeles, California 90089-9176, USA.
Phan
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T
Baumeister
P
P
Roy
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B
Cheriyath
V
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Roy
A L
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Lee
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AS
D016475:3T3 Cells; D051702:Activating Transcription Factor 6; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics*; D002522:Chlorocebus aethiops; D002845:Chromatography / Q000379:methods; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D006367:HeLa Cells; D006360:Heat-Shock Proteins; D006706:Homeostasis; D006801:Humans; D051379:Mice; D018832:Molecular Chaperones / Q000235:genetics*; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; C497112:Atf6 protein, mouse; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors