Topography of polyoma virus-specific giant nuclear RNA molecules containing poly(A) sequences

Abstract

The distribution of viral RNA sequences with respect to poly(A) tracts has been determined for giant polyoma virus-specific nuclear RNA molecules. Polyadenylated nuclear RNA sedimenting faster than 30 S was isolated from polyoma virus-infected cells and cleaved into fragments of various sizes by partial alkaline hydrolysis. Fragments containing poly(A) were separated from nonpolyadenylated RNA. The viral sequence composition of polyadenylated or nonpolyadenylated fragments, and of total polyadenylated giant RNA, was determined by hybridization to 32P-labeled separated strands of specific restriction endonuclease fragments of polyoma virus DNA. The results of this analysis showed that in all polyadenylated giant RNA molecules transcribed from the L DNA strand the portion adjacent to the poly(A) segment hybridizes to the 3′-terminal half of the late region of the viral genome. The next portion of these chains hybridizes to the remainder of the late region, the more distal part hybridizes to the early region, and the portions furthest from the poly(A) contain sequences complementary to the L DNA strand of both early and late regions. This finding shows that polyadenylation of Py giant nuclear RNA is non-random and further suggests that the poly(A)-linked RNA sequence(s) maps within the same region of the viral genome as the poly(A)-linked sequence found in mature cytoplasmic mRNA.