In vitro translation of virion RNA from Moloney murine sarcoma virus

Abstract

Virion RNA of Moloney murine sarcoma virus (Mo-MSV) was translated in the mRNA-dependent reticulocyte lysate and the translation products were analyzed by gel electrophoresis. The major products had apparent molecular weights of 62,000, 37,000, 33,000, 24,000, 18,000, and 15,000. None of these proteins was derived from the helper virus RNA present in our Mo-MSV virion preparations. Immunoprecipitation studies showed that the 62K protein was related to the gag gene product of Moloney murine leukemia virus (Mo-MLV). The 37K, 33K, 24K, 18K, and 15K proteins, on the other hand, were found to be unrelated to either the gag gene or env gene products of Mo-ML V. Tryptic peptide mapping showed that the 37K, 33K, 24K, and 18K proteins had overlapping amino acid sequences. By this criterion the 37K family of proteins was not related to the 62K protein nor to the 15K protein. Likewise, the 15K protein was not related to the 62K protein. Translation of naturally occurring polyadenylated fragments of virion RNA showed that the 62K protein was derived from RNA of genomic length (30 S). The 15K protein was made from RNA of about 25 S, while the 37K, 33K, 24K, and 18K proteins were synthesized from RNAs ranging from 20 to 17 S. On the basis of these results, we have proposed a model for the expression of the genome of Mo-MSV in vitro. The 62K protein would arise from the gag gene at the 5′ end of the Mo-MSV genome. The 15K protein would originate from one of the two pol gene fragments in the Mo-MSV genome. The 37K, 33K, 24K, and 18K proteins would be derived from the src gene of Mo-MSV.