MOLECULAR-CLONING AND CHARACTERIZATION OF DTAF(II)30-ALPHA AND DTAF(II)30-BETA - 2 SMALL SUBUNITS OF DROSOPHILA TFIID

The multisubunit transcription factor TFIID is an essential component of the RNA polymerase II initiation apparatus. Recent studies suggest that TFIID subunits, or TAFs associated with the TATA-binding protein (TBP), play a critical role in modulating transcriptional activation by sequence-specific DNA-binding factors. Thus far, six of the largest TAFs associated with Drosophila TFIID have been cloned and partially characterized. Here, we report the molecular cloning, expression, and subunit interaction specificities of two small molecular mass TAFs. Both dTAF(II)30alpha and dTAF(II)30beta are associated with TFIID via interactions with other TAFs, including dTAF(II)250, dTAF(II)150, and dTAF(II)110. In addition, dTAF(II)30alpha also contacts dTBP. The carboxy-terminal half of dTAF(II)110 was found to contact a short 67-amino-acid region of dTAF(II)30alpha, which is predicted to form two potential alpha-helices, one of which is amphipathic. interestingly, dTAF(II)30alpha also appears to multimerize through its carboxy-terminal region. Although neither dTAF(II)30alpha nor dTAF(II)30beta have been found to interact with specific activators thus far, it is intriguing that both bind other TAFs such as dTAF(II)110 and dTAF(II)150, which are the targets of activation domains. Our studies suggest that both of the small subunits of TFIID play a role in the assembly of the complex and may contribute to the stability of multiple TAF-TAF interactions.