Host restriction of Friend leukemia virus: synthesis and integration of the provirus.

Abstract

Host restriction of exogenous infection by murine leukemia viruses is controlled in vitro predominantly by the murine Fv-1 locus. The mechanism of this-host restriction was investigated by comparing the early events in the replication of N-tropic versus B-tropic Friend leukemia virus in NIH 3T3 cells. These cells, which are Fv-l" in type, are permissive for the N-tropic strain, but nonpermissive for the -tropic strain, which replicates permissively in Balb/c cells. We have studied the synthesis, intracellular location, and molecular form of virusspecific DNA early in replication by means of molecular hybridization with a virus-specific DNA probe. Our results suggest that in the permissive infection viral DNA rapidly becomes integrated with cellular DNA. However, in the nonpermissive infection, although almost equal amounts of both positive and negative strand viral DNA are synthesized, integration of the provirus does not occur.

Human Endogenous Retrovirus K Gag Coassembles with HIV-1 Gag and Reduces the Release Efficiency and Infectivity of HIV-1

“…In future studies, it will be important to confirm these observations using virions and T cells derived from HIV-1-infected patients. Meanwhile, it is tempting to speculate that endogenous retroviruses such as HERV-K, which have existed for a long time in the human genome, might protect the host cells from the threat of exogenous retroviruses, as is the case with Fv1, a remnant of mouse endogenous retrovirus Gag that inhibits the postentry process of MLV infection (29,30,50). In this regard, it will be interesting to determine the mechanism of enhancement of HERV-K expression upon HIV-1 infection and whether HERV-K expression regulates HIV-1 replication in vivo.…”

Synthesis and circularization of N- and B-tropic retroviral DNA Fv-1 permissive and restrictive mouse cells.

“…Results of various previous investigations (13)(14)(15)(16)(17)(18)(19)(20) indicate that Fv-1 restriction occurs intracellularly at an early step of the virus replication cycle. Of particular significance are the observations (i) that, in Fv-1 restricted infection, the quantity of the cellgenome integrated viral DNA is markedly decreased whereas the formation of nonintegrated viral DNA appears to be unaffected (17)(18), and (ii) that transfection by infectious integrated viral DNA is not restricted by the Fv-1 locus of the cell (19,20). These data imply that Fv-1 restriction may occur at or prior to the step of viral DNA integration.…”

TRIM5α mediates the postentry block to N-tropic murine leukemia viruses in human cells

“…Some subtypes of murine leukemia virus (MLV), designated N-tropic (N-MLV) or B-tropic (B-MLV) are blocked in specific mouse strains by the product of the Fv1 gene of mice (6)(7)(8). This block occurs after reverse transcription of the viral genome but before its integration into the host cell genome (9)(10)(11). The Fv1 gene is present only in mice but is related to murine and human endogenous retroviruses and encodes a protein similar to retroviral core (Gag) proteins (12).…”