D. Lee et Jt. Lis, TRANSCRIPTIONAL ACTIVATION INDEPENDENT OF TFIIH-KINASE AND THE RNA-POLYMERASE-II MEDIATOR IN-VIVO, Nature, 393(6683), 1998, pp. 389-392
The carboxy-terminal domain (CTD) of the largest subunit of RNA polyme
rase II becomes multiply phosphorylated by protein kinases during earl
y steps in the gene transcription cycle both in vivo(1) and in vitro(2
). In yeast, the major CTD kinase is a subunit of the general transcri
ption factor TFIIH, and is encoded by an essential gene, KIN28 (ref. 3
). Although the CTD and its phosphorylation are important for transcri
ption(4-6), in vitro studies(7,8) have challenged whether CTD phosphor
ylation is an absolutely required step. The general importance of CTD
phosphorylation by Kin28 for transcription in yeast has been suggested
because, for all genes tested, transcription is inhibited at the non-
permissive temperature in temperature-sensitive kin28 mutants(9,10). H
owever, using such a mutant and a copper-inducible targeted destructio
n method, we show here that transcription of certain genes can be high
ly induced even when cells lack Kin28. We also show that transcription
of these Kin28-independent genes is independent of Srb4 and Srb6, cri
tical components of the CTD-associated transcriptional mediator comple
x(11). These results indicate that there are at least two distinct pat
hways for transcriptional activation: one is dependent on Kin28 and th
e mediator complex, and the other is not.