The Homopolyadenylate and Adjacent Nucleotides at the 3′-Terminus of 30-40S RNA Subunits in the Genome of Murine Sarcoma-Leukemia Virus

Adenosine is the major 3′OH-terminal nucleoside of the 60-70S RNA genome of the murine sarcoma-leukemia virus, its 30-40S RNA subunits, and the poly(A) segments derived by RNase treatment of both RNA species, as determined by periodate oxidation-[3 H]-borohydride reduction. The binding 30-40S RNA to oligo(dT)-cellulose suggests that most viral RNA subunits contain poly(A). The molecular weight of poly(A) derived from viral RNA by digestion with RNase and purified by affinity chromatography is 64,000-68,000, as determined by gel electrophoresis. From the size of poly(A) and the poly(A) content of viral RNA (1.6%), it is estimated that there is about one poly(A) segment for each viral 30-40S RNA subunit. The results of 3′-termini labeling with [3 H]borohydride,in vivo labeling with [3 H]adenosine, and base composition of [32 P]poly(A) indicate that a homopoly(A) segment is located at the 3′-end of a 30-40S RNA subunit. The homogeneous poly(A) segments isolated from RNase T1 digests of 60-70S [32 P]RNA consist of one cytidylate, one uridylate, and about 190 adenylate residues, while those isolated from RNase A digests consist exclusively of adenylate residues. These results indicate that -G(C,U)A190 AOH is the 3′-terminal nucleotide sequence of the viral 30-40S RNA subunits.