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J Virol, April 1998, p. 2697-2707, Vol. 72, No. 4
Department of Biology and Center for
Molecular Genetics, University of California, San Diego, La Jolla,
California 92093-0357
Received 18 November 1997/Accepted 23 December 1997
The human cytomegalovirus (HCMV) UL112-113 promoter represents a
useful model for studying temporal regulation of viral gene expression.
Stimulation of this promoter by the 86-kDa immediate-early protein
(IE86) is controlled by sequences between nucleotides
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Separate DNA Elements Containing ATF/CREB and IE86
Binding Sites Differentially Regulate the Human Cytomegalovirus
UL112-113 Promoter at Early and Late Times in the
Infection
113 and
59,
which include both an ATF/CREB and an IE86 binding site. In transient
assays, the ATF/CREB site is essential, and the IE86 site, although
nonessential, can enhance transcription. With recombinant viruses, we
have assessed the function of these promoter elements in the context of
the viral genome. Transcription from the inserted UL112-113 promoter
shows the same temporal pattern as the endogenous promoter, including
the switch to an upstream RNA start site late in infection. Deletion of
sequences containing the IE86 site results in a decrease in the level
of early transcription and elimination of late transcription. In
contrast, when the ATF/CREB site is deleted, early RNA synthesis is
almost completely abolished, but late transcription is comparable to
that of the wild type, with repositioning of the RNA start site
downstream by the number of nucleotides deleted. Replacement of
sequences between
108 and
95 with the HCMV
cis-repression signal from the major immediate-early promoter had no effect on the level of late RNAs but resulted in the
repositioning of the RNA start site 39 nucleotides upstream. These
results suggest that the ATF/CREB site is functional only at early
times, while sequences containing the IE86 site modulate the level of
early RNAs and may be required for activating late transcription in a
distance-dependent manner.
*
Corresponding author. Mailing address: Department of
Biology, 0357, University of California, San Diego, 9500 Gilman Dr., La
Jolla, CA 92093-0357. Phone: (619) 534-9737. Fax: (619) 534-6083. E-mail: dspector{at}ucsd.edu.
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