Analysis of cells transformed by defective leukemia virus OK10: production of noninfectious particles and synthesis of Pr76gag and an additional 200,000-dalton protein

Nonproducer cells transformed by the defective leukemia virus (DL V), OK10, have been analyzed. Unlike nonproducer cells transformed by the other avian defective leukemia viruses examined so far, the OK10-transformed cells were found to release noninfectious particles. Analysis of these particles indicated that they contained the viral gag gene proteins but lacked env and pol gene products. In agreement with these results analysis of ³⁵S]methio-nine-labeled cell extracts of these nonproducer clones by immune precipitation showed that of the three viral structural protein precursors Pr769^gag, gPr95^env, and Pr180^gag-pol only Pr76^gag could be detected. In addition, a 200,000 molecular weight protein (OK10-200K) was identified in the cell extracts which by using specific antisera, was shown to be related to the gag and pol gene products but not to the product of the env gene. Tryptic peptide analysis of the OK10-200K protein confirmed the immunological data in that the OK10-200K protein was shown to contain all but one of the Pr1809^gag-pol methionine tryptic peptides plus unique peptides which were specific for OK10 and not related to the env gene product. One of these OK10-specific peptides was also shown to comigrate with one of the putative mac gene product tryptic peptides of the MC29-110K protein. These data indicate a novel gene order for a DLV.