A subset of Pr65gag is nucleus associated in murine leukemia virus-infected cells

Abstract

Nuclei of cells infected with Moloney murine leukemia virus (MoMuLV) were examined for the presence of gag proteins. This analysis was performed in conjunction with other studies suggesting a possible role for gag proteins in regulating nuclear events relating to processing and/or transport of viral genomic RNA. We detected Pr65gag and a p30-related protein in a nuclear fraction of infected cells. We also found evidence that a highly conserved amino acid sequence, which is shared by p30 and U1 small nuclear ribonucleoprotein 70-kDa protein, is a component of the nuclear targeting sequence for Pr65gag. Immunoelectron microscopy studies with a monoclonal anti-p12 antibody established that approximately 18% of gag-containing proteins of MoMuLV are located in the nucleus. Such gag-containing proteins from a mutant MoMuLV that lacks N-terminal myristic acid had greater affinity for the nucleus, suggesting that fatty acid acylation of Pr65gag plays a role in overcoming the proposed nuclear transport signal. The possible roles that nuclear gag proteins may play in retroviral replication are discussed.