Nononcogenic deletion mutants of herpesvirus saimiri are defective for in vitro immortalization

Abstract

Herpesvirus saimiri L-DNA sequences between 0.0 and 4.0 map units (4.5 kilobase pairs) are required for oncogenicity; these sequences are not required for replication of the virus. To investigate the basis for the lack of oncogenicity of mutants with deletions in this region and to study the function of this region, we developed a reliable system for in vitro immortalization by herpesvirus saimiri. In contrast to peripheral blood lymphocytes from cotton-top tamarins (Saguinus oedipus) and owl monkeys (Aotus sp.), infection of peripheral blood lymphocytes from common marmosets (Callithrix jacchus) in vitro with herpesvirus saimiri consistently yielded continuously growing lymphoblastoid cell lines. Such cell lines were established using strains of herpesvirus saimiri from group A and group non-A, non-B; however, repeated attempts to immortalize common marmoset peripheral blood lymphocytes using strains from group B were not successful. Common marmoset cell lines immortalized by herpesvirus saimiri were T12+, T8+, T4-, and B1-, indicating that they were derived from suppressor/cytotoxic T lymphocytes. Cell lines could not be established using the nononcogenic mutants 11att and S4, both of which were derived from the group A strain 11 virus. Strain 11att has a spontaneous deletion and S4 has a constructed deletion in the 0.0 to 4.0 map unit region. Constructed strains which had these deleted sequences restored did immortalize common marmoset peripheral blood lymphocytes. Thus, the nononcogenic deletion mutants are defective for immortalization. This system should facilitate attempts to define the sequences responsible for immortalization and to determine their function.

Viral-encoded small RNAs in herpes virus saimiri induced tumors.

“…Three herpes virus saimiri mutants with deletions in this region have been tested previously for transforming activity and oncogenicity (Desrosiers et al, 1985;Desrosiers et al, 1986). The results of these studies correlate interestingly with the genetic origins of the small RNAs (Figure 1).…”

“…pT7.4 is a molecular clone of a 7.4-kbp TaqI fragment derived from herpes virus saimiri sequences from 0.0 to 6.7 map units. Construction of the S4 and KH deletion mutants and their transforming and oncogenic potentials have also been published (Desrosiers et al, , 1985(Desrosiers et al, , 1986; description of the spontaneous deletion in 1latt has also been described previously (Koomey et al, 1984). Mapping of the 2.3and 4.9-kb transcripts in lytically infected OMK cells was accomplished by SI nuclease and exonuclease VII mapping procedures .…”

“…Although not required for replication of the virus, sequences between 0.4 and 4.0 map units (see Figure 1) are required for transformation and oncogenicity. Two mutants (1 latt and S4) with deletions in this region have lost their transforming and oncogenic capacity; restoration of the deleted sequences restored these capacities (Desrosiers et al, 1985;Desrosiers et al, 1986). These mutant strains grow as well as wild-type parental virus in permissive monolayer cells in vitro, are still able to infect New World primates, retain their ability to persistently infect lymphoid cells in vivo and in vitro, and are indistinguishable from the parental virus by a variety of other criteria (Schaffer et al, 1975;Wright, 1978;Desrosiers et al, 1985).…”

Identification of a herpesvirus Saimiri cis-acting DNA fragment that permits stable replication of episomes in transformed T cells

“…70,1996 oriP OF HERPESVIRUS SAIMIRI 1741 2 of strain 11 (2), which is not found within the corresponding regions of strains 484 and 488. Strain 11 deletion mutant viruses with deletions at this region were not affected in either latent or lytic replication (16,43). Further mutational analysis of this dyad symmetry region will be needed to dissect its function.…”

Stimulation of Cyclin-Dependent Kinase Activity and G1- to S-Phase Transition in Human Lymphocytes by the Human T-Cell Leukemia/Lymphotropic Virus Type 1 Tax Protein

“…The wild-type strain from which the vector strain is derived, like all wild-type strains of subgroup A, does not immortalize human cells. The deletion variant has lost some 3.5-kb sequences coding for a protein (STP-A) which transforms rat fibroblasts and induces tumors in nude mice (13,42). Recombinant viruses were isolated and characterized.…”