Correlation of RNA binding affinity of avian oncornavirus p19 proteins with the extent of processing of virus genome RNA in cells

Abstract

The p19 proteins from the Prague C strain of Rous sarcoma virus [RSV-C] avian myeloblastosis virus [AMV], B77 sarcoma virus [B77], myeloblastosis-associated virus-2(0) [MAV-2(0)] and PR-E 95-C virus were purified and their binding affinities for 60S viral RNA were measured by the nitrocellulose filter binding technique. The apparent association constants of the p19 proteins from RSV-C, AMV virus and B77 for homologous and heterologous 60S RNA were similar (1.5 .times. 1011-2.6 .times. 1011 l/mol); those of MAV-2(0) and PR-E 95-C virus were 10-fold lower. The sizes and relative amounts of the virus-specific poly(a)-containing RNA in the cytoplasms of cells infected with RSV-C, MAV-2(0) and PR-E 95-C virus were determined by fractionating the RNA on agarose gels containing methylmercury hydroxide, transferring them to diazobenzyloxymethyl paper and hybridizing them to a 70-nucleotide complementary (c) DNA probe. In cells infected with RSV-C there were 3.4 .times. 106-, 1.9 .times. 106- and 1.1 .times. 106-dalton RNA; in PR-E 95-C virus-infected cells there were 3.4 .times. 106-, 1.9 .times. 106- and 0.7 .times. 106-dalton RNA; and in cells infected with MAV-2(0) there were 3 .times. 106- and 1.3 .times. 106-dalton RNA. Each of these RNA species contained RNA sequences derived from the 5'' terminus of genome-length RNA as evidenced by hybridization with the 5'' 70-nucleotide cDNA. The ratios of subgenomic mRNA to genome-length RNA in cells infected with MAV-2(0) and PR-E 95-C virus were 3 to 5-fold higher than the ratio in cells infected with RSV-C. Thus more processing of viral RNA in infected cells is correlated with lower binding affinities of the p19 protein of viral RNA and the p19 protein apparently conrols processing of viral RNA in cells. [Chicken and quail embryo fibroblasts were used.].