Association of murine leukemia virus gag antigen with extracellular matrices in productively infected mouse cells

Abstract

The gag gene of murine leukemia virus (MuLV) encodes a nonstructural glycosylated polyprotein which appears at the cell surface, in addition to the polyprotein precursor for the virion internal structural proteins. The surface localization of gag nonstructural protein is reported here. Immunofluorescent staining of unfixed monolayers of Moloney MuLV-infected NIH/3T3 cells using anti-p30 serum as the primary antibody revealed an unusual pattern of gag antigen at the attached cell surface: highly organized cable-like structures. Stained cable-like structures were also observed in regions lacking cells or cell processes, which suggested that extracellular gag antigen may be associated with extracellular matrices. This was supported by the fact that detergent treatment of cell monolayers in a manner designed to removed intact cells but preserve extracellular matrices did not affect the cable-like anti-p30 staining patterns. Immunofluorescent staining with anti-gp70 serum revealed a different pattern than the anti-p30 staining, which indicates that surface gag antigen and envelope glycoprotein are not physically associated at the cell surface. Similar staining patterns were observed in mouse cells productively infected with a different strain of MuLV (AKR), and in mink cells productively infected with a mink cell focus-inducing (MCF) derivative of Rauscher MuLV.