Localization of the Polyadenylate Sequences in Messenger Ribonucleic Acid and in the Heterogeneous Nuclear Ribonucleic Acid of HeLa Cells

Abstract

Poly(A) sequences are covalently bound to the 3′ termini of mRNA and many heterogeneous nuclear RNA molecules of HeLa cells. Localization of the poly(A) sequences has been established in these experiments by the observation that a large fraction of the label introduced in the oxidized 2′,3′-cis-glycol groups of these RNAs by sodium borohydride reduction, is recovered in the poly(A) sequences released from these RNAs by ribonucleases A and T1. Similar conclusions were reached by analyses of the 3′ ends of the poly(A) sequences released by these ribonucleases from adenosine-labeled RNAs. These same 3′ end group-labeling techniques have shown that a short poly(A) sequence of about 20 nucleotides found in heterogeneous nuclear RNA is not at the 3′ end.