Different susceptibility of DNA and RNA to cleavage by metal ions

Abstract

METAL ions are required in virtually every phase of genetic information transfer, and they are generally essential components of biochemical processes involving DNA and RNA. Under certain conditions, however, metal ions can have deleterious effects, and one of these, the degradation of polyribonucleotides, is not frequently considered by those who deal with nucleic acids in the presence of metals. No such degradation has been demonstrated with DNA, although it is known1 that DNA, like RNA, is subject to thermal degradation, and therefore can be expected to undergo some degradation also in the presence of metal ions. It is important to understand the relative susceptibility of polydeoxynucleotides and polyribonucleotides to degradation by metal ions to answer the following questions. To what extent is DNA, compared with RNA, vulnerable to metal ion degradation during biochemical experiments? What are the implications for metal ion toxicology? Is the difference in susceptibility to metal hydrolysis sufficient to make possible a quantitative separation of degraded RNA from undegraded DNA in a DNA-RNA mixture? Finally, does this difference in susceptibility reflect differences in the intrinsic stabilities of DNA and RNA, and perhaps throw light on the reason for the evolutionary selection of DNA, rather than RNA, as the favoured bearer of the primary genetic information? These questions can be answered by a comparison of DNA and polyribonucleotide degradation by metal ions using a method of detection sensitive enough to respond to the first break in the macromolecule. © 1975 Nature Publishing Group.