Monospecific immunoprecipitation of murine leukemia virus polyribosomes: identification of p30 protein-specific messenger RNA.

A rabbit antiserum monospecific for the internal structural protein p30 of Moloney murine leukemia virus (M-MuLV) was prepared to immunoprecipitate the polyribosomes synthesizing this protein in producer cells. The antiserum was monospecific for p30 protein as judged by immunodiffusion analysis against purified p30 and total virus protein. In addition, it could specifically precipitate p30 from total virus protein in the presence of cell extracts. Less than 1% of the M-MuLV-specific messenger RNA (mRNA) could be precipitated from purified producer cell polyribosomes when the anti-p30 was used in conjunction with sheep anti-rabbit antiserum. However, considerably more virus-specific mRNA was precipitated when the anti-p30 was used in conjunction with inactivated Staphylococcus aureus, which has binding sites for the antibody. Conditions were obtained where approximately 7% of the virus-specific mRNA in purified polyribosomes was recovered by immunoprecipitation, while normal serum precipitated 10 fold less. The virus-specific mRNA in the immunoprecipitated polyribosomes was 30S-35S in size.