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J. Virol., May 1995, 2786-2793, Vol 69, No. 5
Y Zhao, VR Holden, RH Smith and DJ O'Callaghan
The UL3 protein of equine herpesvirus 1 (EHV-1) KyA strain is a homolog of
the ICP27 alpha regulatory protein of herpes simplex virus type 1 (HSV-1)
and the ORF 4 protein of varicella-zoster virus. To characterize the
regulatory function of the UL3 gene product, a UL3 gene expression vector
(pSVUL3) and a vector expressing a truncated version of the UL3 gene
(pSVUL3P) were generated. These effector plasmids, in combination with an
EHV-1 immediate-early (IE) gene expression vector (pSVIE) and chimeric
EHV-1 promoter-chloramphenicol acetyltransferase (CAT) reporter constructs,
were used in transient transfection assays. These assays demonstrated that
the EHV-1 UL3 gene product is a regulatory protein that can independently
trans activate the EHV-1 IE promoter; however, this effect can be inhibited
by the repressive function of the IE gene product on the IE promoter (R. H.
Smith, G. B. Caughman, and D. J. O'Callaghan, J. Virol. 66:936-945, 1992).
In the presence of the IE gene product, the UL3 gene product significantly
augments gene expression directed by the promoters of three EHV-1 early
genes (thymidine kinase; IR4, which is the homolog of HSV-1 ICP22; and UL3
[ICP27]) and the promoter of the EHV-1 late gene IR5, which is the homolog
of HSV-1 US10. Sequences located at nucleotides -123 to +20 of the UL3
promoter harbor a TATA box, SP1 binding site, CAAT box, and octamer binding
site and, when linked to the CAT reporter gene, are trans activated to
maximal levels by the pSVIE construct in transient expression assays.
Results from CAT assays also suggest that the first 11 amino acids of the
UL3 protein are not essential for the regulatory function of the UL3 gene
product.
Copyright © 1995, American Society for Microbiology
Regulatory function of the equine herpesvirus 1 ICP27 gene product
Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932, USA.
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