TFIIA has activator-dependent and core promoter functions in vivo

The physiological role of TFILA was investigated by analyzing transcription in a yeast strain that contains a TATA-binding protein (TBP) mutant (N2-1) defective for interacting with TFILA. In cells containing N2-1, transcription from a set of artificial his3 promoters depend ent on different activators is generally reduced by a similar extent, indicating that TFILA function is largely nonselective for activators. In addition, TATA element utilization, a core promoter function, is altered at his3 promoters dependent on weak activators. Genomic expression analysis reveals that 3% of the genes are preferentially affected by a factor of 4 or more. Chimeras of affected promoters indicate that the sensitivity to the TFILA-TBP interaction can map either to the upstream or core promoter region. Unlike wild-type TBP or TFILA, the N2-1 derivative does not activate transcription when artificially recruited to the promoter via a heterologous DNA binding domain, indicating that TFILA is important for transcription even in the absence of an activation domain. Taken together, these results suggest that TFILA plays an important role in both activator-dependent and core promoter functions in vine. Further, they suggest that TFILA function may not be strictly related to the recruitment of TBP to promoters but may also involve a step after TBP recruitment.