P. Yalamanchili et al., INHIBITION OF BASAL TRANSCRIPTION BY POLIOVIRUS - A VIRUS-ENCODED PROTEASE (3C(PRO)) INHIBITS FORMATION OF TBP-TATA BOX COMPLEX IN-VITRO, Journal of virology, 70(5), 1996, pp. 2922-2929
Host cell RNA polymerase II (pol II)-mediated transcription is inhibit
ed by poliovirus infection. We demonstrate here that both TATA- and in
itiator-mediated basal transcription is inhibited in extracts prepared
from poliovirus-infected HeLa cells. This inhibition can pe reproduce
d by incubation of uninfected HeLa cell extracts with purified, recomb
inant poliovirus protease, 3C(Pro). Transient-transfection assays demo
nstrate that 3C(Pro), in the absence of other viral proteins, is able
to inhibit cellular pol II-mediated transcription in vivo. Three lines
of evidence suggest that inactivation of TATA-binding protein (TBP) i
s the major cause of inhibition of basal transcription by poliovirus.
First, RNA pol II transcription in poliovirus-infected cell extract is
fully restored by bacterially expressed TBP. Second, addition of puri
fied TBP restores transcription in heat-treated nuclear extracts from
mock- and virus-infected cells to identical levels. Finally, using a g
el mobility shift assay, we demonstrate that incubation of TBP with th
e viral protease (3C(Pro)) inhibits its ability to bind TATA sequence
in vitro. These results suggest that inhibition of pol II transcriptio
n in mammalian cells infected with poliovirus is, at least in part, du
e to the inability of modified TBP to bind pol II promoter sequences.