Transcriptional activation domain of human BTEB2, a GC box-binding factor.

BTEB2 is a GC box-binding transcription factor containing proline-rich and zinc finger domains as transactivation and DNA binding domains, respectively. We have identified a small region in the proline-rich domain indispensable for its transcription-enhancing activity by transfection experiments using various expression plasmids with point mutations or small deletions in the domain. This region comprising about 10 amino acids was relatively hydrophobic and rich in proline and alanine residues. BTEB2 purified from a baculovirus expression system could enhance transcription, depending on the presence of GC boxes in the promoter region of templates in an in vitro transcription assay. BTEB2 deleted of the hydrophobic region, however, lost the transcription-enhancing activity, in confirmation of the above results. Basic transcription factors which possibly interact with BTEB2 were examined. Initiation factors, TFIIB, TFIIE beta, and TFIIF beta as well as the TATA box-binding protein (TBP) were found to interact with BTEB2 when analyzed by in vitro binding experiments, although these interactions could not be attributed to the proline-rich domain. We discussed factors which interact with and transmit the transcriptional activity of the BTEB2 activation domain to basic transcriptional machinery.