Identification of the Regions of Fv1 Necessary for Murine Leukemia Virus Restriction

Abstract

The Fv1 gene restricts murine leukemia virus replication via an interaction with the viral capsid protein. To study this interaction, a number of mutations, including a series of N-terminal and C-terminal deletions, internal deletions, and a number of single-amino-acid substitutions, were introduced into the n and b alleles of the Fv1 gene and the effects of these changes on virus restriction were measured. A significant fraction of the Fv1 protein was not required for restriction; however, retention of an intact major homology region as well as of domains toward the N and C termini was essential. Binding specificity appeared to be a combinatorial property of a number of residues within the C-terminal portion of Fv1.

Origin, antiviral function and evidence for positive selection of the gammaretrovirus restriction gene Fv1 in the genus Mus

“…F/S352 distinguishes Fv1 n and Fv1 nr restriction types, and substitutions at codon 399 alter restriction specificity (5,6). Our analysis also identified positive selection at a position in this region not previously known to affect restriction, 401; its role in restriction may be defined by further mutational analysis.…”

“…The 6 codons identified as being under positive selection included 3 at positions 261, 265, and 270, clustered at the 5Ј end of the MHR, a highly conserved region known to be involved in capsid interactions (18)(19)(20)(21)(22). The other 3 codons identified as being under positive selection were at positions 352, 399, and 401; 2 of these codons, 352 and 399, distinguish the laboratory mouse Fv1 restriction genes (3,5), and substitutions at both of these codons have been shown to contribute to virus restriction (5,6). A third codon, 358, previously implicated in Fv1 restriction in laboratory mice was not identified as being under positive selection; all Fv1 genes except for Fv1 b have K at this site suggesting that the laboratory mouse Fv1 b variant K358E arose fairly recently in Mus.…”

“…The differences include a 9-base in-frame deletion near the N terminus, and 9-aa differences at the C terminus due to the B1 insertion. The rest of the differences are scattered and notably include differences at the 3 amino acid positions (352, 358, and 399) that distinguish Fv1 n , Fv1 b , and Fv1 nr and have been shown to modulate resistance (3,5,6). Residues at these positions for the known restrictive Fv1 alleles are: SKV (Fv1 n ), SER (Fv1 b ), and FKV (Fv1 nr ).…”

“…The major resistance variants of Fv1 differ from one another at 3 amino acid sites in its C-terminal region, and Fv1 b additionally differs from Fv1 n and Fv1 nr at its C terminus due to a 1.3-kb indel (3). Substitutions at the 3 sites and variation at the C terminus all contribute to resistance (5,6). The mechanism of resistance is unknown, but Fv1 typically blocks replication after reverse transcription and before integration.…”

A Trim5-cyclophilin A fusion protein found in owl monkey kidney cells can restrict HIV-1

“…To test the cloned cDNAs, we used a two-color FACS assay originally developed for the study of Fv1 (26,27) and adapted for HIV-1 (25). Human HT1080 cells were transduced with an MLV-based vector encoding the gene to be examined and yellow fluorescent protein, then challenged with tester viruses encoding enhanced GFP.…”