G. Mavankal et al., HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 AND TYPE-2 TAT PROTEINS SPECIFICALLY INTERACT WITH RNA-POLYMERASE-II, Proceedings of the National Academy of Sciences of the United Statesof America, 93(5), 1996, pp. 2089-2094
The Tat-responsive region (TAR) element is a critical RNA regulatory e
lement in the human immunodeficiency virus (HIV) long terminal repeat,
which is required for activation of gene expression by the transactiv
ator protein Tat, Recently, we demonstrated by gel-retardation analysi
s that RNA polymerase II binds to TAR RNA and that Tat prevents this b
inding even when Tat does not bind to TAR RNA, These results suggested
that direct interactions between Tat and RNA polymerase II may preven
t RNA polymerase II pausing and lead to Tat-mediated increases in tran
scriptional elongation. To test this possibility, we performed protein
interaction studies with RNA polymerase II and both the HIV-1 and the
closely related HIV-2 Tat protein, These studies indicated that both
the HIV-1 and HIV-2 Tat proteins could specifically interact with RNA
polymerase II, Mutagenesis of both HIV-1 and HIV-2 Tat demonstrated th
at the basic domains of both the HIV-1 and HIV-2 Tat proteins were req
uired for this interaction. Furthermore, ''far Western'' analysis sugg
ested that the largest subunit of RNA polymerase II was the site for i
nteraction with Tat. The interactions between Tat and RNA polymerase I
I were of similar magnitude to those detected between RNA polymerase I
I and the cellular transcription factor RAP30, which stably associates
with RNA polymerase II during transcriptional elongation, These studi
es are consistent with the model that RNA polymerase II is a cellular
target for Tat resulting in Tat-mediated increases in transcriptional
elongation from the HIV long terminal repeat.