Abstract
Glucose regulated protein 78(grp78) is localized in endoplasmic reticulum, it has calcium binding and chaperone function ability. When cells under stress condition grp78 expression will increase. In mammalian cell, grp78 is a single copy gene and its promoter is functionally redundant which by criterion of DNaseⅠfootprint and gel mobility shift assay binding with nuclear factors. Based on ER-Stress novel promoter regulatory motifs(ERSE) CCAATN9CCACG mediated ER stress response, we identified common cis-regulatory elements on rat grp78 promoter in 9L RBT cells. Using an extensive series of 3’-deletion and CRE-like 8 base pair deletion alone of rat grp78 promoter in a homologous manner. We found that under seven different kinds mechanism drugs treatment, the promoter activity of CRE-like 8 base pair deletion was always significant higher than the intact full length one and Δ21 construct showed the lowest promoter activity that in some treatment even equal or lower than the TATA control construct while addition remove ERSE3 element would promote the promoter activity. Recently, it was reported that overexpression of CREB-Rp (cAMP response element binding protein-related protein) prevents ER stress induced transcription of grp genes mediated by endogenous transactivator. Others reported two new identified Y-box proteins YB-1 and dbpA that repress YY-1 mediated enhanced transcription of grp78 via core element. These lead us to conclude that rat grp78 promoter is strong and many transcription factor binding on its functional redundant element to properly regulate its activity. Some down regulatory transcription factors of CREB-Rp member may bind on CRE-like element. In addition to, negatively control transcription factors YB-1 and dbpA may precisely bind on ERSE3 element that reduce grp78 promoter activity. Moreover, we also showed that stress induces grp78 expression process may all involve in calcium signaling.