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, transcript ion from a set of artificial his3 promoters depend ent on different activat ors is generally reduced by a similar extent, indicating that TFILA functio n is largely nonselective for activators. In addition, TATA element utiliza tion, a core promoter function, is altered at his3 promoters dependent on w eak activators. Genomic expression analysis reveals that 3% of the genes ar e preferentially affected by a factor of 4 or more. Chimeras of affected pr omoters indicate that the sensitivity to the TFILA-TBP interaction can map either to the upstream or core promoter region. Unlike wild-type TBP or TFI LA, the N2-1 derivative does not activate transcription when artificially r ecruited to the promoter via a heterologous DNA binding domain, indicating that TFILA is important for transcription even in the absence of an activat ion domain. Taken together, these results suggest that TFILA plays an impor tant role in both activator-dependent and core promoter functions in vine. Further, they suggest that TFILA function may not be strictly related to th e recruitment of TBP to promoters but may also involve a step after TBP rec ruitment.