Synthesis of Proviral DNA in Inbred Mouse-derived Clones of Cells Expressing Different Fv-1 Phenotypes

Abstract

SUMMARYFormation of proviral DNAs by B-tropic murine leukaemia viruses (MLVs) was examined in N-type and dually permissive mutant cells derived from two inbred mouse strains, DDD and G, both of which are N-type. In the N-type cells, formation of circular proviral DNA was strongly suppressed relative to that of linear DNA. Mutation resulting in loss of the N-type Fv-1 restriction resulted in efficient formation of circular DNA by the previously restricted B-tropic MLV. This showed that Fv-1 restriction and inhibition of closed circular DNA formation were controlled by the same gene. The efficiency of formation of circular proviral DNA by the defective Kirsten murine sarcoma virus was determined by the tropism of the helper virus.The RN A form of the retrovirus genome of murine leukaemia virus (MLV) is transcribed into linear and circular DNA duplexes after infection, and then integrated into the host chromosome. However, it is still unclear which of the free forms of viral DNA is the final precursor of the integrated form (Varmus, 1983). Study of the restriction exercised by the Fv-1 locus of mice has been found appropriate for studying this problem. The formation of circular but not linear DNA was suppressed in Fv

Benzo[a]pyrene Activates the Human p53 Gene through Induction of Nuclear Factor κB Activity

“…Third, another reason might be dependent on the cell line tested. There is a report suggesting at least two NIH 3T3 cell lines of different origins circulating in the world (45). Indeed, some researchers identified p50 in NIH 3T3 cells binding to NF-B sequence (46), while others did not (47).…”

Analysis of Fv-1 restriction in two murine embryonal carcinoma cell lines and a series of differentiated derivatives

“…The step in MuLV replication sensitive to Fv-1 is at or before the integration step which forms the provirus and may involve aspects of reverse transcription and/or integration (Jolicoeur & Rassart, 1980;Yang et al, 1980;Chinsky & Soiero, 1981 ;Iwamoto et al, 1985). It is not known how the Fv- (Gisselbrecht et al, 1974;Hartley & Rowe, 1975;Yoshikura et al, 1982), cells in culture are thought also to express Fv-1 constitutively (Hartley et al, 1970).…”

Development and characterization of an Fv-1-sensitive retrovirus-packaging system: single-hit titration kinetics observed in restrictive cells

“…Fv-1 restriction is relative rather than absolute and is evident in cell culture as a 30to 1,000-fold reduction in virus infectivity for cells of the restrictive genotype (19,35). The sensitive step in viral replication is not known precisely but clearly involves some aspect of reverse transcription or integration or both (9,20,23,42). Typically, linear DNA is synthesized normally but circular forms and integrated molecules are greatly reduced or not detected.…”