YIN-YANG-1 ACTIVATES THE C-MYC PROMOTER

Previous studies on the murine c-myc promoter demonstrated that a ubiq uitously present protein, common factor 1 (CF1), bound at two sites lo cated -260 and -390 bp from the Pl transcription start site. CF1 has b een purified to near homogeneity and shown to be identical to the zinc finger protein Yin-yang 1 (YY1) as judged by similarity of molecular weight and other biochemical properties, immunological cross-reactivit y, and the ability of recombinant YY1 to bind to CF1 sites. In cotrans fection experiments, YY1 is a strong activator of transcription from c -myc promoter-based reporters. Furthermore, in murine erythroleukemia cells, overexpressed YY1 causes increased levels of c-myc mRNA initiat ed from both major transcription initiation sites of the endogenous c- myc gene.