Cleavage of Homopolyribonucleotide Strands by Aromatic Reductones and Its Regulation by Nucleic Acid Bases

Abstract

The breakage activities of aromatic reductones, such as catecholamines, on homopolyribo-nucleotides were investigated by gel electrophoretic methods. A comparison of poly C breakage activities of aromatic reductones in the presence of Cu²⁺ revealed that epinephrine had the strongest effect, followed by the order, dopamine, norepinephrine, pyrocatechol and dopa. Adrenochrome had no breakage activity. The pattern of molecular distribution of homopolyribonucleotide fragments produced by treatment with the aromatic reductone-Cu²⁺ mixture suggested that the cleavage of homopolyribonucleotide strands by aromatic reductones occurred at random.
The mean breakage number on poly C induced by the epinephrine-Cu²⁺ mixture increased with reaction time. The breakage reaction was remarkably enhanced depending on the concentration of epinephrine and Cu²⁺. In the absence of Cu²⁺ no detectable cleavage occurred. The cleavage reaction proceeded quickly at pH 7 but was weakened in both the acidic and alkaline pH regions. Among various kinds of metallic ions, Cu²⁺ exhibited an overwhelmingly strong effect on the catalysis of the breakage reaction.
Although Ni²⁺, Co²⁺, Mg²⁺ and Fe³⁺ also had weak effects, Fe²⁺ Mn²⁺, Zn²⁺ and Pb²⁺ had no detectable effects. All homopolyribonucleotides used were broken by the epinephrine-Cu²⁺ mixture but the sensibility to the breakage was weakened in the order of poly C, poly U, poly A and poly G, in accordance with the degree of epinephrine oxidation at later reaction periods.
The breakage of poly C by the epinephrine-Cu²⁺ mixture was suppressed by the co-existence of cytosin or adenine, suggesting that nucleic acid components can regulate the degree of nucleic acid scission by aromatic reductones through the regulation of the oxidation reaction of aromatic reductones in the presence of Cu²⁺.