ANALYSIS OF THE ROLE OF TFIIE IN TRANSCRIPTIONAL REGULATION THROUGH STRUCTURE-FUNCTION STUDIES OF THE TFIIE-BETA SUBUNIT

The general transcription factor TFIIE plays important roles at two di stinct but sequential steps in transcription as follows: preinitiation complex formation and activation (open complex formation), and the tr ansition from initiation to elongation. The large subunit of human TFI IE (TFIIE alpha) binds to and facilitates the enzymatic functions of T FIIH, but TFIIE also functions independently from TFIIH. To determine functional roles of the small subunit of human TFIIE (TFIIE beta), del etion mutations were systematically introduced into putative structura l motifs and characteristic sequences. Here we show that all of these structures that lie within the central 227-amino acid region of TFIIE beta are necessary and sufficient for both basal and activated transcr iption. We further demonstrate that two C-terminal basic regions are e ssential for physical interaction with both TFIIE alpha and single-str anded DNA, as well as with other transcription factors including the D rosophila transcriptional regulator Kruppel. In addition, we analyzed the effects of the TFIIE beta deletion mutations on TFIIH-dependent ph osphorylation of the C-terminal domain of RNA polymerase II and on wil d type TFIIE beta-driven basal transcription. Both responsible regions also mapped within the essential 227-amino acid region. Our results s uggest that TFIIE engages in communication with both transcription fac tors and promoter DNA via the TFIIE beta subunit.