Covalently bound ribonucleotides in crab d(A-T) polymer.

In addition to the known 3% of G + C residues, samples of purified crab d(A-T) polymer from Cancer borealis contained small amounts (< 3%) of RNA. Aliquots of d(A-T)n were digested with crude venom, and the resultant nucleosides were analyzed by high pressure liquid chromatography (HPLC); up to one-half of all guanosine was rG. Other aliquots were exhaustively digested with purified pancreatic DNase I to produce 88% dinucleotides. HPLC fractionation of this dinucleotide mixture into individual components revealed the presence of three mixed dinucleotides: -dC-rG, -dT-rA, and -dT-rG. A third aliquot of d(A-T)n was hydrolyzed overnight with 0.3 M KOH at 37 degrees C; approximately equal amounts of ribomononucleotides (predominantly containing purines) and deoxyribomononucleotides (predominantely containg thymine) were produced. KOH-hydrolyzable ribonucleotides accounted for one-third to one-half of the total RNA. The rest of the ribonucleotides remained with longer d-fragments, presumably as 3'(2')-terminal nucleotides (. . .d-d-d-rp). It was concluded that crab d(A-T) polymer from C. borealis contains 1 to 3% of dispersed, covalently bound ribonucleotides. The results also suggest that the sugar specificity of DNase I may be limited to a nucleotide following the cleavage.