Self-Organization of Ribosomal RNA

RNA, like protein, is capable of forming compact tertiary structures. Transfer RNA has become the first known example of unique tertiary structures of the polyribonucleotides. High molecular weight RNAs have been less studied in this respect, but their ability to acquire compact conformations at sufficient ionic strength and especially in the presence of Mg2+ and polyamines suggested long ago their specific folding into tertiary structures (Spirin, 1963). Electron microscopy study of the isolated ribosomal RNAs in compact conformation has demonstrated their unique shape (Vasiliev et al., 1978; Vasiliev and Zalite, 1980). Determinations of ribosomal RNA primary structures have allowed to predict and to give an experimental proof of the main patterns of their secondary structures, which are formed by complementary base-pairing of polynucleotide chain sections; long-range base-paired interactions indicated the formation of a unique domain structure of the ribosomal RNA (reviewed by Brimacombe et al., 1983). The self-organization of secondary and tertiary structure of the ribosomal RNAs seems to be a prerequisite and a conformational basis for the assembly and the function of the ribosome.