TATA box occupancy in the SV40 transcription elongation complex

in order to gain insight into requirements for template activation and comm itment in mammalian transcription, TATA site occupancy was measured in nati ve SV40 viral transcription complexes that were in the process of transcrip tion elongation at the time of cell lysis. This was accomplished by quantif ying resistance to restriction enzyme digestion of transcription complexes in nuclear lysate. The rate of cleavage at the TATA site of the late gene i n the native complex was slower than that of a bare DNA control, both for w ild-type virus and for a virus containing a TATA consensus sequence. These results suggest that the TATA site in the transcription elongation complex in vivo is occupied with transcription factor TBP/TFIID. When considered in light of previous work, these findings support a model in which transcript ion activation involves reinitiation from a promoter that contains both act ivator and TFIID bound in a stable complex. (C) 2001 Academic Press.