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Mol. Cell. Biol., Oct 1996, 5393-5399, Vol 16, No. 10
SW French, MC Schmidt and JC Glorioso
Latency-active promoter 2 (LAP 2) is a TATA-less promoter in herpes simplex
virus type 1 (HSV-1) that can express genes during viral latency. Four
regions of LAP2 are protected from DNase I digestion in vitro by either
HeLa cell nuclear extracts or purified Sp1. Transient gene expression
assays of LAP2 substitution mutants demonstrate that two of the regions
protected by Sp1 and three other regions protected by nuclear extract are
important for promoter function. The mutation causing the most significant
reduction in expression alters a stretch of 23 thymidine residues (T23)
that binds a protein with several properties common to high-mobility-group
(HMG) proteins. The T23 binding activity is heat stable, can be inhibited
by poly(dA- dT).poly(dA-dT), and is inhibited by minor-groove-binding
drugs. Antiserum directed against HMG I(Y) blocked the formation of one of
the DNA-protein complexes on the T23 oligonucleotide, suggesting that a
protein antigenically related to HMG I(Y) binds to LAP2 in vitro. Direct
evidence of HMG I(Y) involvement in LAP2 function is provided by the
findings that recombinant HMG I(Y) protein facilitates Sp1 binding to LAP2
in mobility shift assays and that antisense HMG I(Y) RNA specifically
inhibits LAP2 function in vivo. These results suggest that DNA structure
may be an important determinant of the activity of a promoter that is
capable of escaping the global shutoff of transcription that occurs during
viral latency.
Copyright © 1996, American Society for Microbiology
Involvement of a high-mobility-group protein in the transcriptional activity of herpes simplex virus latency-active promoter 2
Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pennsylvania 15261, USA.
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