Common sets of nuclear factors binding to the conserved promoter sequence motif of two coordinately regulated ER protein genes, GRP78 and GRP94.

The GRP78 and GRP94 are two constitutively expressed ER resident proteins that are coordinately induced in response to stress conditions. The control of their induction is at the transcriptional level. We have previously demonstrated that the GRP78 and the GRP94 promoters share a common regulatory domain which is highly conserved. We report here that within this 36 bp promoter region is a CG/CAAT and a GC-rich sequence motif which are important for basal level and induced expression of the gene. Gel mobility shift assays with HeLa nuclear extracts and the conserved element from GRP78 and GRP94 show two shared, specific protein-DNA complexes. By ultraviolet cross-linking, the sizes of the proteins labeled in the slower-migrating complex are 210-, 110-, a doublet at 90/92- and 70 kD, and in the faster-migrating complex, protein species of about 55 kD. The formation of the second complex can be inhibited by competition with the coding strand of the conserved GRP element in a sequence specific manner. In addition, the Ku autoantigen which is abundant in HeLa cell extracts also binds. The sizes of the nuclear factors binding to the GRP78 and GRP94 conserved promoter elements are strikingly similar, providing further evidence that the two genes are coordinately regulated by common trans-acting factors.