Absence of Polyadenylic Acid from Reovirus Messenger Ribonucleic Acid

Reovirus single-stranded RNA isolated from mouse L cells pulse-labeled with radioactive RNA precursors for various intervals at different times after infection does not contain detectable poly(A) sequences.All three size classes of viral mRNA, like reovirus double-stranded genome RNA, have cytosine at their 3' termini.The results indicate that the presence of poly(A) sequences in reovirus single-stranded RNA is not required for translation or conversion to doublestranded viral RNA.Reovirus contains, in addition to 10 double-stranded genome RNA segments, approximately 1200 molecules per virion of oligoadenylic acid (1, 2).The oligo(A) is 10 to 15 bases long.Some oligo(A) molecules are terminated with 5'-adenosine monophosphate, although 5'-di-and triphosphates have also been observed (2).Reovirus double-stranded RNA (3), singlestranded mRNA (4-6), and some virion-associated oligonucleotides (1, 2) are terminated with 5'-guanosine di-or triphosphates.The nature of its 5' termini suggested that the oligo(A) bearing 5'-monophosphate (1) may arise as a result of nucleolytic cleavage from a larger RNA.The presence of poly(A) sequences covalently linked to the 3' termini of mRNA's from eukaryotic cells (7-13) and viral RNAs (14-23) led us to consider the possibility that some of the "free" oligo(A) in reovirus resulted from a cleavage of poly(A) regions from reovirus mRNA.In an effort to elucidate the origin and role of the reovirus oligo(A), we have isolated from reovirus-infected cells the three size classes of single-stranded viral mRNA, 70% of which is polysome-associated (4).We have tested for the presence of covalently linked poly(A) and identified the 3'-terminal base. MATERIALS AND METHODS Virus and CellsReovirus type 3 (Dearing strain) was propagated in mouse L-929 cells (26).Stock cultures of poliovirus (type 1, Mahoney strain) and vesicular stomatitis virus (Indiana strain) were generous gifts from Dr.