The 5' terminal structures of murine α and β globin messenger RNA

The 5' terminal structures of murine α and β globin mRNA were determined after incubating cells of the erythropoiety spleens of mice with [methyl ³H]methionine. Globin mRNA was obtained from total cellular RNA by oligo(dT) cellulose chromatography followed by elution of mRNA from formamide gels after electrophoresis. The globin mRNA was then hydrolyzed with KOH or digested with a combination of R Ase T₂ and bacterial alkaline phosphatase, and 5' terminal structures were isolated by DEAE cellulose chromatography. The methylated nucleotides of these 5' structures were determined following digestion with specific ribonucleases and bacterial alkaline phosphatase. Analyses of mRNA fractions enriched for either α or β mRNA gave similar results. Our data indicate that murine α and β globin mRNAs are identical through the first three nucleotides and that partial dimethylation exists at the second position: m⁷(5') [m⁶A(m)/A(m)]pC(m)pNp.