J Mol Biol. 1998 Mar 27;277(2):179-97. Unique Identifier : AIDSLINE
The transactivator protein Tat stimulates transcriptional elongation
from the HIV-1 LTR. One mechanism by which Tat increases HIV-1
transcription is by interacting with RNA polymerase II and TFIIH to
increase phosphorylation of the polymerase C-terminal domain. Recent
studies indicate that specific elongation factors may also be required
to modulate Tat function. Here, we used biochemical analysis and in
vitro transcription assays to identify cellular factors required for Tat
activation. This analysis resulted in the purification of a cellular
factor Tat-CT1 which is a human homolog of the yeast transcription
factor SPT5. Immunodepletion of Tat-CTl from HeLa extract demonstrated
that this factor was involved in transcriptional activation by Tat.
However, the absence of this factor from HeLa extract did not prevent
transcriptional activation by VP16. These findings are consistent with a
model in which Tat-mediated effects on transcriptional elongation are
mediated in part by the action of the human homolog of the yeast
transcription factor SPT5. Copyright 1998 Academic Press Limited.
*Fungal Proteins/METABOLISM *Gene Products, tat/METABOLISM
*HIV-1/METABOLISM *Nuclear Proteins/METABOLISM *Saccharomyces
cerevisiae/METABOLISM *Trans-Activators/METABOLISM *Transcription
Factors/METABOLISM