Terminal sequence studies of high-molecular-weight ribonucleic acid. The 3' termini of rabbit globin messenger ribonucleic acid.

Haemoglobin mRNA isolated from EDTA-treated polyribosomes has an apparent molecular weight of 120000-180000 estimated by condensation with (3)H-labelled isoniazid after periodate oxidation. Analysis of the ribonuclease digests of isoniazid-labelled RNA by paper electrophoresis and column chromatography enables the amount of contaminating 18S, 7S, 5S and 4S RNA to be estimated, and a corrected molecular weight of globin mRNA as the acid is 161000 or 500 nucleotides in length. This molecule contains two groups of 3'-terminal sequences in equal yield; G-Y-A(6) and G-Y-A(7) in the ratio 3:2, and G-N(9-16)-Y-A(2) and G-N(9-16)-Y-N(3) in the ratio 3:2. The significance of these sequences is discussed in relation to the poly(A) content of globin mRNA, the specificity of the sequences, and possible function in processing and biosynthesis of mRNA.