SUMMARYTransfection experiments with plasmids containing immediate early (IE) genes of herpes simplex virus type l (HSV-1) have previously demonstrated a role for the IE polypeptide Vmw110 (ICP0) in stimulating expression from plasmid-encoded early gene promoters. To gain further insights into the function of Vmw110 we isolated a deletion mutant specifying a truncated form of the polypeptide which had been shown to be inactive in transfection assays. This mutant, dl1403, contained a 2 kb deletion within both the TRL and IRL copies of the Vmw110 gene, and encoded a polypeptide consisting of the original N-terminal 105 amino acids followed by 56 amino acids specified by a reading frame not used by Vmw110. dl1403 was able to replicate and produce plaques on baby hamster kidney (BHK) cells but the yield of infectious virus was 20-to 100-fold lower than obtained with wild-type HSV-1.
SUMMARYCells infected with herpes simplex virus type I (HSV-I) DNA by the calcium phosphate precipitation technique produce virus which leads to the formation of plaques (Graham, Veldhuisen & Wilkie, 1973). In the study reported here we show that treatment of cell monolayers with dimethyl sulphoxide (DMSO) solutions after infection with DNA-calcium phosphate complexes leads to a considerable increase in the number of plaques obtained. The conditions for this enhancement of infectivity have been optimized for baby hamster kidney (BHK) cells, and increases in plaque numbers of over Ioo-fold have been obtained. The treatment appears to increase the proportion of cells which respond to DNA infection by initiating plaque formation, and results in a large increase in the measured specific infectivity of HSV-I DNA. DMSO causes similar (but quantitatively different) responses in various other cell lines infected with HSV-I DNA. BHK cells infected with either virus particles, or virus DNA by the DEAE-dextran technique (Laithier & Sheldrick, I975), do not exhibit this massive enhancement following exposure to DMSO.
Cells. BHK-21 clone 13 cells (10) were grown in Eagle medium supplemented with 10% calf serum. Virus. The type 1 parent strain 17 and temperature-sensitive (ts) mutants used in this study, tsA,-B,-D,-E,-H,-K, and-S, have previously been described (3, 11). Syn+ forns tsH syn and tsS syn were isolated by M. Brown (unpublished data). The type 2 parent strain, HG52, and mutants tsl,-5,-6, and-11 were described by Timbury (18) and Halliburton and Timbury (8). tsll PAA' is a phosphonoacetic acid-resistant derivative of tsll (Timbury, unpublished data). The isolation and genome structures of the recombinants used in this study are summarized in Table 1 and Fig. 1. The previously undescribed recombinants B x 5 (7), B x 5 (10), B x 6 (17), 17+ x llr (1), and F x 5 (12) were generated and plaque purified by the 624
Evidence was recently presented that herpes simplex virus type 1 (HSV-1) immunoglobulin G (IgG) Fc receptors are composed of a complex containing a previously described glycoprotein, gE, and a novel virus-induced polypeptide, provisionally named g70 (D. C.
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