Marker rescue of temperature-sensitive mutants by defective DNA of herpes simplex virus type 1

Molecular genetics of vaccinia virus: demonstration of marker rescue

Two genomic variants of vaccinia virus isolated from serially propagated stocks were used to demonstrate marker rescue. The smaller (S variant) virus contains a 6.3 megadalton (MDal) deletion of unique DNA sequences present in the 123-MDal larger (L variant) virus. The deletion was mapped at 6.85 MDal from the left terminus of the genome, just outside of the inverted terminal repetition. Rescue of the unique deleted DNA sequences by infectious S variant virus was obtained in CV-1 cells by using the calcium orthophosphate precipitation technique of intact or restriction endonuclease-treated L-variant DNA. Restriction fragments that overlapped the deletion allowed marker rescue, but restriction of the L-variant DNA within the unique deleted sequences gave negative results. Restriction endonuclease analysis of the DNA obtained from twice-plaque-purified recombinant virus derived from the rescue of overlap donor fragments gave a restriction pattern identical to that of L-variant virus, indicating that the donor DNA was inserted into the rescuing virus by double recombination. No amplification of the unique sequences was observed from intact L-variant DNA in the absence of infectious S-variant virus, suggesting that deproteinized vaccinia DNA is noninfectious and that the donor DNA was neither integrated into the host DNA nor present as an episomal structure. By using 1 microgram of intact L-variant DNA per CV-1 monolayer in a 6-cm Petri dish, approximately 1--5% of the plaques contained the L-variant genotype, and the dose--response curve was essentially linear from 0.1 to 2 microgram of DNA.

Fine-structure mapping and functional analysis of temperature-sensitive mutants in the gene encoding the herpes simplex virus type 1 immediate early protein VP175

Herpes simplex virus (HSV)-specific proteins fall into at least three kinetic classes whose synthesis is sequentially and coordinaely regulated. Temperature-sensitive (ts) mutants of one complementation group (1-2) are defective in the transition from immediate early to early and late protein synthesis. To elucidate the function of the 1-2 gene product in the HSV type 1 replicative cycle, nine ts mutants in this group were mapped by fine-structure analysis and characterized members of the group lie within the terminally repeated sequences of the S region of the genome. Fine-structure genetic and physical mapping permitted the mutations to be ordered within these sequences. Because it has been shown that the message for VP175 and the DNA template specifying this protein extend beyond the limits of the physical map of the mutations, it follows that the mutations must lie within the structural gene for VP175. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that most members of the group overproduced the immediate early proteins VP175, -136, -110, and -63 and markedly underproduced early and late proteins at the nonpermissive temperature. In temperature shiftup experiments, it was fund that the synthesis of early and late proteins ceased, whereas the synthesis of immediate early proteins began again. Thus, it is postulated that VP175 is (i) involved in the transition from immediate early to early protein synthesis, (ii) requird continuously to maintain early protein synthesis, (iii) autoregulated, acting to inhibit immediate early protein synthesis.

Ultrastructural characterization of an early, nonstructural polypeptide of herpes simplex virus type 1

An immunoperoxidase procedure was employed to study the expression of a large-molecular-weight, virus-induced polypeptide (VP175; molecular weight, 175,000) at the light and electron microscopic levels in Vero cells infected with herpes simplex virus type 1 or with tsB2, a DNA-negative, temperature-sensitive mutant of herpes simplex virus type 1. In cells infected with herpes simplex virus type 1 and in cells infected with tsB2 at the permissive temperature (34 degrees C), VP175 was found within the nucleus. The protein was detected as early as 2 h postinfection and, by 3 h postinfection, was generally distributed in a marginated pattern contiguous with, and extending from, the inner lamella of the nuclear membrane. At 6 h postinfection, protein accumulations were dispersed throughout the nucleus, and, by 9 h postinfection, these accumulations tended to be localized in a marginated pattern near the nuclear membrane. It was also noted that, at 9 h postinfection, under permissive conditions, VP175 was not found in association with nucleocapsids or enveloped particles. In contrast, in cells infected with tsB2 at the nonpermissive temperature (39 degrees C) and harvested at 6 or 9 h postinfection, accumulations of VP175 were identified not only within the nucleus, but also within the cytoplasm in the form of annular or globular aggregates. These aggregates consisted of a granular matrix and were not bound by membranes.