Wheat embryo ribonucleates. XII. Formal characterization of terminal and penultimate nucleoside residues at the 5′-ends of 'capped' RNA from imbibing wheat embryos

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Abstract
N2,N2,7-Trimethylguanosine, not previously detected as a component of plant RNA, is shown to be present in the RNA which is isotopically labeled when dry wheat embryos imbibe water in a medium that contains [methyl-3H]methionine. N2,N2,7-Trimethylguanosine and 7-methylguanosine are released as part of capped oligonucleotides when the isotopically labeled RNA from imbibing wheat embryos is subjected to hydrolysis by RNase T2. By way of contrast with the capped RNA of animal cells, 5''-terminal cap structures (m7Gppp- and m32,2,7Gppp-) in the capped RNA from the higher plant organism are not bonded to penultimate O2''-methylnucleoside constituents. In an allied study, it was found that recovery of poly(A)-rich RNA from dry wheat embryos depends on the inclusion of sodium dodecyl sulfate (SDS) in phosphate-buffered (pH 6.8) phenolic emulsions. Recovery of poly(A)-rich RNA from dry wheat embryos does not depend on the inclusion of SDS in Tris(hydroxymethyl)aminomethane buffered (pH 9.0) phenolic emulsions.
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