Globin Messenger Precursor RNA in Duck Immature Red Blood Cells

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Abstract
A procedure is described for the chromatographic analysis of RNA under fully denaturing conditions on cross‐linked Sepharose. Chromatography of DNA · RNA hybrids, poly(C) · poly(G) hybrids and complexes of poly(C) · hnRNA on Sepharose CL in pure formamide at 46°C leads to denaturation and strand separation of the hybrid structures. Using this procedure, nuclear RNA from duck immature red blood cells was resolved according to molecular size and assayed for the presence of globin mRNA sequences by hybridization with complementary DNA. Two size classes of putative globin mRNA precursor molecules were detected at an elution position corresponding to 14–18 S and 23–28 S. As judged from chromatographic analysis on poly(U)‐Sepharose, about 70% of the 14–18‐S globin precursor RNA is polyadenylated while only 11% of the putative 23–28‐S precursor RNA has a poly(A) tract. Inhibition of transcription by actinomycin D and pulse‐chase experiments indicate a half‐life of less than 7.5 min for these precursor RNA species.