K. Masternak et R. Wittek, CIS-ACTING AND TRANS-ACTING ELEMENTS INVOLVED IN REACTIVATION OF VACCINIA VIRUS EARLY TRANSCRIPTION, Journal of virology, 70(12), 1996, pp. 8737-8746
We have previously shown that transcription from the vaccinia virus 7.
5K early promoter is reactivated late in infection (J. Garces, K. Mast
ernak, B. Kunz, and R. Wittek, J. Virol. 67:5394-5401, 1993). To ident
ify the sequence elements mediating reactivation, we constructed recom
binant viruses harboring deletions, substitutions, or insertions in th
e 7.5K promoter or its flanking regions, The analysis of these viruses
showed that sequences both upstream as well as downstream of the tran
scription initiation site contribute to reactivation of the 7.5K promo
ter. We tested whether reactivation could be explained by a high affin
ity of vaccinia virus early transcription factor to reactivated promot
ers. Bandshift experiments using purified protein showed that promoter
s which bind the factor,vith high affinity in general also have high e
arly transcriptional activity, However, no correlation was found betwe
en affinity of the factor and reactivation. Interestingly, overexpress
ion of recombinant early transcription factor in vaccinia virus-infect
ed cells resulted in a shutdown of late transcription and in reactivat
ion of promoters, which are normally not reactivated.