On the bias of the distribution of the 2′- O-methylribonucleotide constituents of yeast transfer RNA

Abstract

Preparations of transfer RNA (tRNA) were isolated from bakers' yeast and studied with respect to the differential distribution of their 2′- O-methylribonucleotide constituents. For this purpose, the alkali-stable dinucleotide fraction mNpNp, which amounted to 2.3±0.1 % of the RNA phosphorus, was isolated and examined for the relative abundance of the various nucleotides and their O-methyl derivatives. The individual dinucleotides were separated from each other and estimated quantitatively. Twelve out of the sixteen possible major dinucleotide combinations were found. The study of the composition of the mNp and Np fractions and the investigation of the relative frequencies of the individual dinucleotides revealed remarkable deviations from randomness which are discussed in detail. In addition, the distribution of the end-group nucleotides terminating with a 5′-phosphate group was determined in the tRNA specimens employed. The identity of the methylpentose moiety of the alkali-stable dinucleotides was confirmed as 2- O-methylribose by comparison with an authentic specimen.