HUMAN TAF(PI)250 INTERACTS WITH RAP74 - IMPLICATIONS FOR RNA-POLYMERASE-II INITIATION

Accurate and regulated transcription by RNA polymerase II requires the assembly of an initiation complex involving multiple protein-DNA and protein-protein interactions. A key event is binding of TFIID, a complex consisting of TBP and associated factors (TAFs) to the template DNA. The TAF subunits of TFIID early out diverse functions critical for transcription, including specific contact with enhancer proteins and binding to core promoter DNA. However, the role of TAFs in RNA polymerase II-mediated transcription initiation and cross talk with other basal factors remains poorly characterized. Here, we report the specific interaction of TAF(II)250 with RAP74, an essential subunit of the basal transcription factor IIF. Using various in vitro binding assays we have mapped recognition interfaces between TAF(II)250 and RAP74. In vivo complementation of a temperature-sensitive TAF(II)250 cell line reveals that the RAP74 interaction is critical for cell viability. Because TFIIF is thought to be responsible for binding and recruiting RNA polymerase II, the ability of TAF(II)250 to interact selectively with RAP74 is likely to contribute a critical contact for the assembly of an active transcription complex.