CLONING AND EXPRESSION OF HUMAN TAF(II)250 - A TBP-ASSOCIATED FACTOR IMPLICATED IN CELL-CYCLE REGULATION

BASAL transcription by human RNA polymerase II requires the coordinate action of several ancillary factors (TFIIA-J)1 and can be regulated by various promoter-specific DNA binding proteins. An additional class of factors, called coactivators, are dispensable for basal transcription but are indispensable for regulation by transcriptional activators2-4. Biochemical studies established that some coactivators are associated with the TATA-binding protein (TBP) to form the TFIID complex3-6. We therefore set out to define the relationship between TBP and these TBP-associated factors (TAFs). Here we describe the cloning, expression and properties of the first human TAF, hTAF(II)250. The hTAF(II)250 gene is identical to a gene, CCG1 (refs 7, 8), implicated in cell-cycle progression. Recombinant hTAF(II)250 binds directly to TBP both in vitro and in yeast, and participates in the formation of the TFIID complex. This largest TAF may therefore play a central role in TFIID assembly by interacting with both TBP and other TAFs, as well as serving to link the control of transcription to the cell cycle.