Human TATA-binding protein-related factor-2 (hTRF2) stably associates withhTFIIA in HeLa cells

The TATA-binding protein (TBP)-related factor TRF1, has been described in D rosophila and a related protein, TRF2, has been found in a variety of highe r eukaryotes. We report that human (h)TRF2 is encoded by two mRNAs with com mon protein coding but distinct 5' nontranslated regions. One mRNA is expre ssed ubiquitously (hTRF2-mRNA1), whereas the other (hTRF2-mRNA2) shows a re stricted expression pattern and is extremely abundant in testis. In additio n, we show that hTRF2 forms a stable stoichiometric complex with hTFIIA, bu t not with TAFs, in HeLa cells stably transfected with flag-tagged hTRF2. N either recombinant human (rh)TRF2 nor the native flag.hTRF2-TFIIA complex i s able to replace TBP or TFIID in basal or activated transcription from var ious RNA polymerase II promoters. Instead, rhTRF2, but not the flag.hTRF2-T FIIA complex, moderately inhibits basal or activated transcription in the p resence of rhTBP or flag TFIID. This effect is either completely (TBP-media ted transcription) or partially (TFIID-mediated transcription) counteracted by addition of free TFIIA. Neither rhTRF2 nor flag.hTRF2-TFIIA has any eff ect on the repression of TFIID-mediated transcription by negative cofactor- 2 (NC2) and neither substitutes for TBP in RNA polymerase III-mediated tran scription.