Organization of Sequences in Avian Globin mRNA

Abstract

Formamide polyacrylamide gel electrophoresis shows that chicken globin mRNA contains about 650 nucleotides. Since only 435 of these code for globin, a further 215 were not translated, and their function and position are not known. Poly(A) at the 3'' terminus accounts for 45-50 of these untranslated nucleotides. The 3'' untranslated region of chicken globin mRNA is at least 90 nucleotides in length. This minimal estimate is based on data derived from hybridization of defined lengths of chicken globin c[complementary]DNA to rabbit globin mRNA. The percentage of avian globin cDNA sequences which hybridize to rabbit globin mRNA is directly proportional to the length of the cDNA in each case. This relationship holds for lengths of cDNA from 115-620 nucleotides. The low percentage homology for short cDNA molecules is not due to their being short per se. In homologous mRNA excess hybridizations (chicken cDNA/chicken mRNA), all cDNA preparations were completely protected from S1 nuclease digestion. There is probably a greater evolutionary divergence in the 3'' untranslated region of chicken and rabbit globin mRNA when compared with the coding regions of these molecules. The combined data is used to formulate a regional map of chicken globin mRNA.