Precursor polyproteins of moloney murine leukemia virus

Abstract

Four cell clones infected with and producing Moloney murine leukemia virus were examined with regard to the synthesis of viral internal structural proteins or group antigens (‘gag’), the reverse transcriptase (‘pol’) and the viral envelope proteins (‘env’). The size, properties and antigenic determinants of the various precursors were, in general, similar to those precursors that have been characterized in Rauscher murine leukemia virus-infected cells. However, the mobility of the Moloney envelope precursor was significantly different from that observed in the Rauscher murine leukemia virus system. The Moloney murine leukemia virus envelope precursor had an apparent molecular weight of 85 000 (gPr85 env) compared to 90 000 (gPr90 env) for the Rauscher murine leukemia virus precursor. In addition one of the Moloney ‘gag’ precursors (Pr85 gag) comigrated with gPr85 env in sodium dodecyl sulfate polyacrylamide gels. Comigration of these precursors was demonstrated by analysis of immunoprecipitates with monospecific antisera directed against either p30 or gp69/71 and by labeling studies using [ 3H]glucosamine, which has been shown to label the glycoprotein precursor. The mobilities of the Moloney virus ‘gag-pol’ precursor read-through proteins in sodium dodecyl sulfate polyacrylamide gels were very similar to the Rauscher murine leukemia virus Pr200 gag-pol except in one case. Processing of the Moloney murine leukemia virus precursors occurred in the presence of cycloheximide at concentrations that inhibit protein synthesis 98%. However, the processing of precursor Pr65 gag and Pr200 gag-pol was partially inhibited by cycloheximide treatment. No such effect was observed with the processing of gPr85 env.