The nucleotide sequence of the 5′ untranslated region of human γ-globin mRNA

Abstract

The nucleotide sequence of the entire 5′ untranslated region of human γ-globin mRNA has been determined. This was accomplished by analyzing complementary DNA (cDNA) synthesized form the mRNA with reverse transcriptase. The cDNA was labeled at its 3′ end with ³²P using terminal deoxynucleotidyl transferase, digested with the restriction endonuclease Hae III and the end-labeled fragment isolated and sequenced by the method of Maxam and Gilbert. Including the initiation codon AUG, the 5′ untranslated region of human γ-globin mRNA contains 57 nucleotides, compared to 4l in α- and 54 in β- globin mRNA. There is very little homology between α and γ sequences in the 5′ region. There is considerable homology between β- and γ-globin mRNAs in the regions proximal and distal to the initiation codon, but the entire sequence shows less homology than the human and rabbit β-globin mRNAs. The hexanucleotide sequence CUUCUG is found near the 5′ ends of all three human globin mRNAs, suggesting a possible role of this sequence in ribosomal binding. Both guanosine and cytidine were found at the 19th nucleotide position from the 5′ end of the γ mRNA. We believe this heterogeneity arises from the difference in nucleotide sequence between the ^Aγ and ^Gγ loci.