Intramolecular interaction of yeast TFIIB in transcription control

The general transcription factor TFIIB is a key component in the eukaryotic RNA polymerase II (RNAPII) transcriptional machinery. We have previously s hown that a yeast TFIIB mutant (called YR1m4) with four amino acid residues in a species-specific region changed to corresponding human residues affec ts the expression of genes activated by different activators in vivo. We re port here that YR1m4 can interact with several affected activators in vitro . In addition, YR1m4 and other mutants with amino acid alterations within t he same region can interact with TATA-binding protein (TBP) and RNAPII norm ally. However, YR1m4 is defective in supporting activator-independent trans cription in assays conducted both in vitro and in vivo. We further demonstr ate that the interaction between the C-terminal core domain and the N-termi nal region is weakened in YR1m4 and other related TFIIB mutants. These resu lts suggest that the intramolecular interaction property of yeast TFIIB pla ys an important role in transcription regulation in cells.