Elongation of DNA complementary to the 5' end of the avian sarcoma virus genome by the virion-associated RNA-dependent DNA polymerase

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Abstract
RNA-dependent DNA synthesis in a virion-associated reaction is dependent upon the detergent concentration used for disruption of the virion. The Triton X-100 concentration affected the elongation of the initially synthesized DNA complementary to the last .apprx. 100 nucleotides at the 5'' end of the RNA (cDNA100). Elongation of cDNA100 increased with time of incubation at the optimal detergent concentration; this process was retarded at higher detergent concentrations. At the optimal detergent concentration, elongated DNA was of low chemical complexity; extension of cDNA100 occurred at a unique site on the RNA. Higher than optimal detergent concentrations resulted in nonspecific elongation and in DNA of high chemical complexity, as shown by oligopyrimidine tract analysis. Actinomycin D inhibited the elongation of cDNA100 at the optimal detergent concentration. The nature of elongation process was elucidated by analysis of DNA synthesized in a virion-associated reaction in the presence of bacteriophage Q.beta. RNA. At the optimal detergent concentration DNA complementary only to avian sarcoma virus RNA was synthesized; at higher concentrations DNA was copied from both avian sarcoma virus and Q.beta. RNA. Apparently elongation mechanism of cDNA100 is affected by the detergent concentration and elongation is unspecific at higher than optimal detergent concentrations. The mechanism by which the nonionic detergent stimulates DNA synthesis was not yet resolved. Other factors in addition to DNA polymerase are involved in elongation of cDNA100.