Herpes simplex virus type 2 mutagenesis: characterization of mutants induced at the hprt locus of nonpermissive XC cells.

Abstract

. 66:259-265, 1985). A series of 17 independent mutants were isolated after viral infection together with 12 spontaneous noninfected mutants to characterize the nature of the mutations induced by the virus at the molecular level. The DNA of the mutants isolated after viral infection was probed with cloned HSV-2 fragments representing the entire genome. In these mutants, no authentic HSV-2 hybridization could be detected. This was indicative of a mechanism of mutagenesis which did not require the permanent integration of viral sequences in the host genome. The structure of the hprt gene was determined by the method of Southern (J. Mol. Biol. 98:503-517, 1975), and the level of hprt mRNA was analyzed by Northern blots. Except for the identification of one deletion mutant in each of the two groups, the HPRT-clones showed no evidence of alteration in their hprt gene. A total of 7 of 12 spontaneous mutants and 11 of 15 mutants isolated from the infected population transcribed an hprt mRNA of the same size and abundance as did the wild-type cells. Thus, the majority of the mutants seemed to have a point mutation in their hprt structural gene.Interestingly, the proportion of the different types of mutations was similar in the two groups of mutants. This analysis revealed that HSV-2 infection did not increase the frequency of rearrangements but rather that it probably induced a general increase of the level of mutations in the cells. This type of response is thought to be compatible with the biology of the virus, and the possible mechanisms by which HSV-2 induces somatic mutations in mammalian cells are discussed.Defined regions of the herpes simplex virus type 2 (HSV-2) genome can transform rodent cells in vitro (12,20), but the existence of a viral oncogene responsible for the maintenance of the transformed state has been questioned because of the lack of evidence that a specific viral sequence was retained in these cells (13). In addition, transformation by HSV is less efficient (13,20,21) than what is generally observed with viral oncogenes (3, 29). These considerations suggested that the role of the virus was transient and led to the hypothesis that HSV acts as a mutagen (13,17,42,61). The first evidence that HSV could cause mutations came from observations that infection often results in fragmentation and pulverization of cellular chromosomes (4,16,45,57). It was subsequently shown by Schlehofer and zur Hausen (41) that infection of human permissive rhabdomyosarcoma cells by inactivated HSV-1 could result in an increased mutation frequency at the hypoxanthine phosphoribosyltransferase (hprt) locus. In a previous report, we made use of the XC cell line, which is not permissive for HSV-2, to demonstrate that intact viral particles could increase the frequency of HPRT-mutants by factors ranging from 2.4 to 10.3 (38). Other DNA viruses such as simian virus 40 and adenovirus type 2 can cause mutations at several loci in nonpermissive infections (14,27,28,50,52,60). However, the nature of the virally induced mutations h...

Analysis of cyclin-dependent kinase activity after herpes simplex virus type 2 infection.

“…Cycling cells and cells expressing high levels of CDC are more efficiently killed by cytotoxic T cells (Greenberg & Litchfield, 1995), suggesting this would be advantageous for the virus in vivo. Since DNA damage induces a G # arrest (Maltzman & Czyzyk, 1984 ;Zhan et al, 1993) and HSV infection leads to DNA damage (Kulomaa et al, 1992 ;Pilon et al, 1986 ;Schlehofer & zur Hausen, 1982), DNA damage may also activate cellular factors which block mitosis. The major findings in this study are that following infection, Rb was phosphorylated, CDK2 activity was increased, and steady-state levels of cyclin A were increased.…”

Herpes Simplex Virus Type 1 and Bovine Herpesvirus 1 Latency

“…For example, HSV induces DNA damage even in the absence of productive infection (27,56,93,206,229). DNA damage is a potent stimulus for apoptosis (246).…”

Hypomethylation of host cell DNA synthesized after infection or transformation of cells by herpes simplex virus.

“…However, multiple studies on the actual method of transformation have produced a variety of possible properties of the virus which could be involved in transformation. These features include the structure of the transforming DNA involving the presence of insertion sequences (16) or altered repeat elements (22), biological carcinogenesis such as mutation or gene amplification (35,39), or even the involvement of the ribonucleotide reductase gene whose large and small subfragments map within the DNA sequences involved in the induction of morphological transformation (reviewed by Macnab [26]). What is reasonably clear is that viral DNA encoding a transforming protein is not retained in the cells (9,15).…”