Characteristics of avian sarcoma virus strain PRCIV and comparison with strain PRCII-p

Avian sarcoma virus strain Poultry Research Centre IV (PRCIV) (J. G. Carr and J. G. Campbell (1958)Brit. J. Cancer12, 631–635) is highly oncogenic in chickens and transforms chicken embryo fibroblasts in culture. It is defective in replication, unable to code for complete functional products of the three essential viral genes gag, pol, or env. Nonproducing cells transformed by PRCIV lack the transforming protein of Rous sarcoma virus, pp6^src but synthesize a new transformation-specific protein of 170,000 MW. This P170 contains partial gag sequences, probably at its N-terminus and transformation-specific, cell-derived sequences, probably in the C-terminal portion of the molecule. In two-dimensional tryptic peptide maps P170 of PRCIV is indistinguishable from the transformation-specific protein P170 of the previously described PRCII-p (M. L. Breitman, J. C. Neil, C. Moscovici, and P. K. Vogt (1981)Virology108, 1–12). Both P170 proteins also contain all but one tryptic peptide of the transformation-specific gag-linked protein P105 found in cells transformed by avian sarcoma virus PRCII. The P170 proteins of PRCIV and PRCII-p have an associated tyrosine-specific kinase activity similar to P105 of PRCII. All three agents, PRCII, PRCII-p, and PRCIV, belong to class II of avian sarcoma viruses. In cells transformed by PRCIV or PRCII-p secondary gag-linked transformation-specific proteins of less than 170,000 MW are sometimes seen, but limited in vivo and in vitro passage of the viruses shows the P170 to be a stable characteristic of PRCIV and PRCII-p transformation. The genomic RNA of PRCIV and PRCII-p sediments at 30 S corresponding to a size of about 6.1 kilobases.