A NEGATIVE COFACTOR CONTAINING DR1 P19 MODULATES TRANSCRIPTION WITH TFIIA IN A PROMOTER-SPECIFIC FASHION/

An activity that modulated the relative levels of transcription from t he adenovirus major late promoter (MLP), and the immunoglobulin heavy chain mu promoter (mu) was purified as a 90-kDa factor, This factor is suggested to be a heterotetramer of two subunits: a 20-kDa polypeptid e identical to the previously described Dr1/p19 and a novel 30-kDa pol ypeptide. The Dr1/p19 protein has been characterized as a repressor of transcription, and the 30-kDa protein is related to a recently identi fied yeast gene proposed to encode a repressor of transcription, The 9 0-kDa factor forms a complex with TATA-binding protein on DNA and at h igh concentrations of both factors protects over a 150-base pair regio n around the promoter from DNase I cleavage, The conformation of this complex as assayed by footprinting analysis is altered by the transcri ption factor TFIIA on the MLP but not on the mu promoter. Similarly, T FIIA reverses the repression of transcription by the 90-kDa factor on the MLP but not on the mu promoter, Thus, the interactions of TATA-bin ding protein, TFIIA, and the 90-kDa factor are promoter-specific.