The 5'-terminal structure of poly(A)-containing RNA of soybean seeds.

Poly(A)-containing RNA from soybean seeds was isolated by affinity chromatography on poly(U)-Sepharose. Translation of poly(A)-containing RNA was inhibited by the addition of m7GMP. Treatment of the poly(A)-containing RNA with periodate followed by aniline (a chemical removal of 5'-terminal m7G) resulted in a marked reduction of mRNA activity. mRNA activity of the treated RNA was partially restored when S-adenosyl methionine (SAM) was included the wheat germ cell-free system. End groups of the poly(A)-containing RNA were labeled by oxidation with periodate and reduction with [3H]borohydride. Analysis of nuclease digests of 3H-labeled poly(A)-containing RNA showed the existence of materials with a charge between --2 and--3 and/or between --3 and--4 which contain pyrophosphate linkages. These results imply the presence of 5'-terminal capped structures, m7G(5')PPp(5')N and m7G(5')PPP(5')Nm, in soybean poly(A)-containing RNA.