H. Xiao et al., THE UPSTREAM ACTIVATOR CTF NF1 AND RNA-POLYMERASE-II SHARE A COMMON ELEMENT INVOLVED IN TRANSCRIPTIONAL ACTIVATION/, Nucleic acids research, 22(11), 1994, pp. 1966-1973
The carboxy-terminal domain (CTD) of the largest subunit of RNA polyme
rase II consists of tandem repeats of a heptapeptide with the consensu
s YSPTSPS. It has been shown that the heptapeptide repeat interacts di
rectly with the general transcription factor TFIID. We report here tha
t the CTD activates transcription when fused to the DNA-binding domain
of GAL4. More importantly, we find that the proline-rich transcriptio
nal activation domain of the CCAAT-box-binding factor CTF/NF1 contains
a sequence with striking similarity to the heptapeptide repeats of th
e CTD. We show that this CTD-like motif is essential for the transcrip
tional activator function of the proline-rich domain of CTF/NF1. Delet
ion of and point mutations in this CTD-like motif abolish the transcri
ptional activator function of the proline-rich domain, while natural C
TD repeats from RNA polymerase II are fully functional in place of the
CTD-like motif. We further show that the proline-rich activation doma
in of CTF/NF1 interacts directly with the TATA-box-binding protein (TB
P), and that a mutation in the CTD-like motif that abolishes transcrip
tional activation reduces the affinity of the proline-rich domain for
TBP. These results demonstrate that a class of proline-rich activator
proteins and RNA polymerase II possess a common structural and functio
nal component which can interact with the same target in the general t
ranscription machinery. We discuss the implications of these results f
or the mechanisms of transcriptional activation in eucaryotes.