CELL-CYCLE-DEPENDENT PHOSPHORYLATION OF THE BASAL TRANSCRIPTION FACTOR RAP74

In this report, cell-cycle-dependent effects of TFIID on other basal t ranscription factors were investigated. We purified TFIlD fractions fr om HeLa cells synchronized in the S/G2 phases and in early G1 phase, a nd show that RAP74 is phosphorylated more highly by the S/G2 phase TFI ID fraction than by the early G1 phase TFIID fraction. Further analyse s using deletion mutants of RAP74 revealed that amino acid residues 20 6-256 are phosphorylated by the TFIID fraction. Reconstitution of in v itro transcription activity indicates that the cell-cycle-dependent ph osphorylation of RAP74 increases TFIIF transcription activity. (C) 199 7 Federation of European Biochemical Societies.