A MAMMALIAN RNA-POLYMERASE-II HOLOENZYME CONTAINING ALL COMPONENTS REQUIRED FOR PROMOTER-SPECIFIC TRANSCRIPTION INITIATION

The protein kinase MO15/CDK7 has recently been shown to be associated with the general transcription factor TFIIH and to be capable of phosp horylating the RNA polymerase II carboxy-terminal domain. Here, we sho w that a monoclonal MO15/CDK7 antibody coimmunoprecipitates, from a ra t liver nuclear extract, all components of the RNA polymerase II trans cription apparatus required for initiation at the albumin and adenovir us major late promoters. The immunoprecipitate includes RNA polymerase II, TFIID, TFIIB, TFIIH, TFIIF, and TFIIE, but is devoid of transcrip tional activator proteins, such as HNF1, HNF4, and C/EBP alpha. The fi nding of an autonomously initiating RNA polymerase II holoenzyme in ma mmalian cells suggests conceptual similarities between transcription i nitiation in prokaryotes and eukaryotes.