Evidence for multiple forms and partial resolution of rabbit reticulocyte alpha- and beta-globin messenger RNA by gel...

Isoelectric focusing in polyacrylamide gels has been used to fractionate and characterize RNAs from rabbit reticulocytes with major emphasis on globin mRNA. Reticulocyte 18S and 28S RNAs banded essentially as single components, well separated from each other and from the multiple forms of tRNA. By contrast, mRNA was resolved into a number of major and minor components. These bands were shown to contain intact globin mRNA by translation in a messenger-dependent cell-free protein synthesizing system. One major band was enriched slightly in alpha-globin mRNA and a second major band was enriched considerably in beta-globin mRNA. Reticulocyte supernatant mRNA, containing predominantly alpha-globin messenger, demonstrated only one major component which banded at the same position as the alpha-enriched band from total mRNA. Little of this material behaved as beta mRNA either by its focusing profile or by its translation products. Globin mRNA fractions with high and low 3' poly(A) contents also demonstrated differences in focusing distribution profiles. Although the basis for separating RNA by this technique has not been established, our results suggest that isoelectric focusing may offer a new approach to fractionation and characterization of specific mRNA species.