Critical role of the second stirrup region of the TATA-binding protein for transcriptional activation both in yeast and human.

We previously identified three TATA-binding protein (TBP) point mutations (L114K, L189K, and K211L) that have severe effects on transcriptional activation by acidic activators, but no effect on basal transcription, in a yeast-derived TBP-dependent in vitro transcription system (Kim, T. K., Hashimoto, S., Kelleher, R. J., III, Flanagan, P. M., Kornberg, R. D., Horikoshi, M., and Roeder, R. G. (1994) Nature 369, 252-255). These activation defects were also demonstrated in vivo in yeast cells (Lee, M., and Struhl, K. (1995) Mol. Cell. Biol. 15, 5461-5469). Here, the transcriptional activities of these and other TBP mutations were examined in human by both in vitro and in vivo assays. Mutations L189K and E188K, which lie in the second stirrup region of TBP, show defective activation by acidic activators both in yeast and human. Somewhat surprisingly, mutations L114K and K211L have almost no demonstrable effect on activation by acidic activators in human, in contrast to their severe effects on defective activator responses in yeast. The implications of these results for TBP structure and function are discussed.