Post‐transcriptional Modifications of Oat Coleoptile Ribonucleic Acids

Abstract

Evidence is presented for the occurrence of 5''-terminal capping structure in poly(A)-rich RNA from oat coleoptile tissue. Similar to the cap structures in mRNA from other eukaryotic organisms, the 5'' terminus of these oat coleoptile RNA molecules consists of 7-methylguanosine joined 5'' to 5'' with the adjacent (penultimate) nucleoside by means of 3 phosphate groups in 2 pyrophosphate linkages. The penultimate nucleoside contains primarily purine bases, but small amounts of pyrimidines (cytidine) are also detectable. Some monophosphorylated 5''-termini were also detected, but they appear to occur as a result of RNA degradation. In addition to the 5'' cap, oat RNA molecules are also post-transcriptionally modified with a low frequency of N6-methylations of internal adenosines.