Identification of the cis-Acting Endoplasmic Reticulum Stress Response Element Responsible for Transcriptional Induction of Mammalian Glucose-regulated Proteins

Abstract

When unfolded proteins accumulate in the endoplasmic reticulum (ER), transcription of glucose-regulated proteins (GRPs) representing ER-resident molecular chaperones is markedly induced via the unfolded protein response (UPR) pathway. In contrast to recent progress in the analysis of yeast UPR, both cis-acting elements and transactivators responsible for mammalian UPR have remained obscure. Here, we analyzed the promoter regions of human GRP78, GRP94, and calreticulin genes and identified a novel element designated the ER stress response element (ERSE). ERSE, with a consensus of CCAATN 9 CCACG, was shown to be necessary and sufficient for induction of these GRPs. Using yeast onehybrid screening, we isolated a human cDNA encoding a basic leucine zipper (bZIP) protein, ATF6, as a putative ERSE-binding protein. When overexpressed in HeLa cells, ATF6 enhanced transcription of GRP genes in an ERSE-dependent manner, whereas CREB-RP, another bZIP protein closely related to ATF6, specifically inhibited GRP induction. Endogenous ATF6 constitutively expressed as a 90-kDa protein was converted to a 50-kDa protein in ER-stressed cells, which appeared to be important for the cellular response to ER stress. These results suggest that, as in yeast, bZIP proteins are involved in mammalian UPR, acting through newly defined ERSE.

Roles of CHOP/GADD153 in endoplasmic reticulum stress

“…36,42 These sequences are highly homologous with other ERSEs identified in the promoters of the BiP, GRP94, PDI and calreticulin (CRT) genes. 8,43 CHOP AARE was identified to be an essential motif for amino-acid activation of the CHOP promoter. 44 This sequence has weak homology with C/EBP-and ATF-binding sites.…”

“…6 The second response is upregulation of genes encoding ER chaperone proteins such as BiP/GRP78 and GRP94, enzymes including protein disulfide isomerase (PDI) and peptidyl-prolyl isomerase, and structural components of the ER including sarcoplasmic ER Ca 2 þ -ATPase 2 (SERCA2), to increase the protein-folding capacity in ER. [7][8][9] In addition to these genes, recent studies revealed that genes involved in translational recovery, amino-acid import, glutathione biosynthesis and protection against oxidative stress are also upregulated. 10 In a later phase, components of ER-associated degradation (ERAD), including ER degradation-enhancing a-mannosidase-like protein (EDEM), are transcriptionally induced to eliminate misfolded proteins in the ER by the ubiquitin-proteasome system.…”

BRCA1 and BRCA2 as molecular targets for phytochemicals indole-3-carbinol and genistein in breast and prostate cancer cells

“…Luciferase reporters driven by the wild-type endoplasmic reticulum stress-response element (ERSEwt-Luc), a mutant ERSE (ERSEmut-Luc, a negative control), and the ERSE-II element (ERSEII3x-Luc) in the pGL3 vector were generously provided by Dr Kazutoshi Mori (HSP Research Institute, Kyoto Research Park, Kyoto, Japan) (Yoshida et al, 1998;Yamamoto et al, 2004). A CHOP (C/EBP homologous protein) promoter-luciferase reporter in the pGL3 vector (CHOP-Luc) was provided by Dr Pierre Fafournoux (Unite de Nutrition et Metabolisme Proteique, INRA de Theix, Saint Genes Champanelle, France) (Bruhat et al, 2000).…”

RNA interference mediated knockdown of the KDEL receptor and COPB2 inhibits digestion and reproduction in the parasitic copepod Lepeophtheirus salmonis

“…Disturbing this process by gene knock down might trigger ER stress and thus induce the UPR. One of the proteins known to be upregulated by the UPR is the ER chaperone calreticulin (Yoshida et al, 1998). To check if the ER stress system is activated by the knock down of LsKDELR and LsCOPB2, the mRNA expression levels of the salmon louse homologue of calreticulin (LsCalr) were assessed by qRT-PCR (Fig.…”