Association of murine leukemia virus Pol with virions, independent of Gag-Pol expression

During the replication cycle of murine leukemia virus (MLV), Pol is normall y synthesized as part of a Gag-Pol fusion protein. In this study, the abili ty of free MLV Pol to be incorporated into virions was examined. When MLV G ag and MLV Pol were coexpressed from separate plasmids in cells, reverse tr anscriptase (RT) activity associated with Gag core particles at a slightly lower level than did RT activity generated from wild-type Gag-Pol expressio n. Particles produced in this manner were somewhat less infectious than tho se produced with wild-type Gag-Pol. A smaller amount of MLV Pol also associ ated with heterologous human immunodeficiency virus type 1 Gag cores.