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J. Virol., Mar 1997, 1784-1793, Vol 71, No. 3
P Cheung, B Panning and JR Smiley
Globin genes are normally expressed only in erythroid cell lineages.
However, we found that the endogenous alpha-globin gene is activated
following infection of human fibroblasts and HeLa cells with herpes simplex
virus (HSV), leading to accumulation of correctly initiated transcripts
driven by the alpha-globin promoter. The alpha1- and alpha2- globin genes
were both induced, but expression of beta- or zeta-globin genes could not
be detected. Experiments using HSV mutants showed that null mutations in
the genes encoding the viral immediate-early proteins ICP4 and ICP22
reduced induction approximately 10-fold, while loss of ICP0 function had a
smaller inhibitory effect. Transient transfection experiments showed that
ICP0 and ICP4 are each sufficient to trigger detectable expression of the
endogenous gene, while ICP22 had no detectable effect in this assay. ICP4
also strongly enhanced expression of transfected copies of the
alpha2-globin gene. In contrast, the adenovirus E1a protein did not
activate the endogenous gene and inhibited expression of the plasmid-borne
alpha2-globin gene. Previous studies have led to the hypothesis that
chromosomal alpha-globin genes are subject to chromatin-dependent
repression mechanism that prevents expression in nonerythroid cells. Our
data suggest that HSV ICP0 and ICP4 either break or bypass this cellular
gene silencing mechanism.
Copyright © 1997, American Society for Microbiology
Herpes simplex virus immediate-early proteins ICP0 and ICP4 activate the endogenous human alpha-globin gene in nonerythroid cells
Institute for Molecular Biology and Biotechnology, Department of Biology, McMaster University, Hamilton, Ontario, Canada.
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