Ribonucleotide sequences non-adjacent to poly(A) participate in the poly(A)-protein complex in 15S duck globin mRNP particles.

The study of the interaction between mRNA and proteins in the polyribosomal 15 S duck globin messenger ribonucleoprotein complex showed that proteins protect specific mRNA sequences against digestion by the nonspecific micrococcal nuclease (Nucleic Acids Research 6 (8) 2787, 1979). Here we report the isolation of the poly(A)-protein RNP complex from nuclease digested 15 S mRNP by two different methods: sucrose gradient sedimentation and oligo(dT)-cellulose chromatography. We show by fingerprint analysis, that aprt from the periodically fragmented poly(A) segment, mRNA sequences adjacent and non-adjacent to the poly(A) segment are protected by the poly(A) binding proteins against nuclease digestion. The duck globin poly(A)-protein RNP complex, with a sedimentation coefficient between 7 S and 10 S, shows a characteristic protein composition, with a major 73,000 MW polypeptide and some minor components. The results are discussed in view of a dynamic ribonucleoprotein structure.