Fig. 5.

The minimal sequence required for IAα promoter repression corresponds to transacting factor binding sites. A: CAT assays were performed using extracts of R8RP.3 cells transfected with pIAα(890)CAT and its derivatives containing site-specific deletions of the regions from −541 to −492 (pIAαΔ541/492CAT) and −840 to −810 (pIAαΔ840/810CAT). B: PCR-based mutagenesis was used to selectively delete the sequences between −839 and −828 from the 890 bp IAα promoter, and the resulting mutant promoter was cloned into pCATbasic to form pIAα(Δ839/828)CAT. Shown are representative experiments with the average percent conversion of the nonacetylated to the acetylated form of chloramphenicol and the standard error calculated from the number of experiments indicated in parentheses.