Effect of interferon on mouse leukaemia virus (MuLV). V. Abnormal proteins in virions of Rauscher MuLV produced in the presence of interferon.

Interferon treatment of JLSV-6 cells chronically infected with Rauscher MuLV leads to the formation of non-infectious particles ('interferon' virions) containing the structural proteins coded by the env and gag genes as well as additional virus polypeptides. The major glycoprotein detected in the control virions is gp71, but 'interferon' virions contain in addition an 85K mol. wt. (gp85) glucosamine-containing, fucose-deficient glycoprotein. This is recognized by antiserum to MuLV and may be related to env pr85. Surface iodination of intact virions indicates that gp71 and gp85 are the two major components of the external envelope. However, whereas in control virions gp71 associates with p15E (gp90), this complex was not detected in 'interferon' virions. Analysis of radio-labelled (3H-amino acids or iodinated) proteins from disrupted 'interferon' virions revealed the presence of 65K, 55K, 40K, 20K and 12K mol. wt. polypeptides which could be precipitated with antiserum against MuLV. There was a distinct difference in the patterns of incorporation of pulse-labelled 3H-amino acid polypeptides into virions in the presence and absence of interferon. Those polypeptides labelled in the presence of interferon and recovered in the extracellular virions in a chase with interferon appeared to have substantially fewer copies of p30 and more of gag pr55 polypeptide than the controls. These results indicate that in the presence of interferon there are changes in the proteolytic cleavage associated with virion assembly.