The Association of DNA and RNA with Membranes

This chapter describes the membrane association of nucleic acids. It presents supportive data in this regard and discusses the speculative aspects of the association of DNA and RNA with cell membranes. The membrane association of chromosomal DNAs appears to be a universal phenomenon, observed in prokaryotes, eukaryotes, viruses, and extrachromosomal DNAs. Many techniques are employed to study this DNA-membrane association. Electron microscopy (EM) and autoradiography provide morphological data. A variety of biochemical procedures including the preferential association of DNA with lipoprotein-rich extracts, selective salt extraction, density gradient centrifugation, incorporation of thymidine analogs (for example, bromodeoxyuridine), and labeling with radioactive DNA precursors is also presented. Extensive biochemical and EM studies show that RNA is present as an integral membrane component and as a substructural part of membrane-bound ribosomes. Membrane RNA is relatively insensitive to RNase, is soluble in organic solvents, and is most readily extracted with acidified water or hot (60^°C) phenol or other standard solvents following treatment of the membrane with sodium dodecyl sulfate. This membrane-associated RNA (mbrRNA) may play a variety of roles, including ribosome binding via rRNA–mbrRNA association, stabilization of mRNA by membranes, and translation of mRNA on membrane-bound ribosomes.