CELL CYCLE-DEPENDENT REGULATION OF RNA-POLYMERASE-II BASAL TRANSCRIPTION ACTIVITY

Regulation of transcription by RNA polymerase II (pol II) in eukaryoti c cells requires both basal and regulatory transcription factors. In t his report we have investigated in vitro pol II basal transcription ac tivity during the cell cycle by using nuclear extracts from synchroniz ed Hela cells. It is shown that pol II basal transcription activity is low in the S and Ga phases and high in early G1 phase and TFIID is th e rate limiting component of pol II basal transcription activity durin g the cell cycle. Further analyses reveal that TFIID exists as a less active form in the S and G2 phases and nuclear extracts from S and G2; phase cells contain a heat-sensitive repressor(s) of TATA box binding protein (TBP). These results suggest that pol II basal transcription a ctivity is regulated by a qualitative change in the TFIID complex, whi ch could involve repression of TBP, during the cell cycle.