The mammalian endoplasmic reticulum stress response element consists of anevolutionarily conserved tripartite structure and interacts with a novel stress-inducible complex

When mammalian cells are subjected to calcium depletion stress or protein g lycosylation block, the transcription of a family of glucose-regulated prot ein (GRP) genes encoding endoplasmic reticulum (ER) chaperones is induced t o high revels. The consensus mammalian ER stress response element (ERSE) co nserved among grp promoters consists of a tripartite structure CCAAT(N-9)CC ACG, with N being a strikingly CC-rich region of 9 bp, The ERSE, in duplica te copies, can confer full stress inducibility to a heterologous promoter i n a sequence-specific but orientation-independent manner. In addition to CB F/NF-Y and YY1 binding to the CCAAT and CCACG motifs, respectively, we furt her discovered that an ER stress-inducible complex (ERSF) from HeLa nuclear extract binds specifically to the ERSE, Strikingly, the interaction of the ERSF with the ERSE requires a conserved GGC motif within the 9 bp region. Since mutation of the GGC triplet sequence also results in loss of stress i nducibility, specific sequence within the 9 bp region is an integral part o f the tripartite structure. Finally, correlation of factor binding with str ess inducibility reveals that: ERSF binding to the ERSE alone is not suffic ient; full stress inducibility requires integrity of the CCAAT, GGC and CCA CG sequence motifs, as well as precise spacing among these sites.