The Identification of the Ribosomal Rna Cistron by Sequence Complementarity, Ii. Saturation of and Competitive Interaction at the Rna Cistron

Abstract

The presence of a sequence in DNA complementary to homologous ribosomal RNA is indicated by experiments described in a preceding paper.1 The data showed that a hybrid complex resistant to RNAase is formed when mixtures of ribosomal RNA and denatured DNA from the same cell are heated and then subjected to a slow cool.2 When DNA from a heterologous source is substituted, no such complex is observed. The specific pairing of ribosomal RNA with a complementary sequence in DNA leads to the following two predictions: (1) The ratio of RNA to DNA in the specific complex should approach a maximum value at levels indicating the involvement of a minor fraction of the DNA;(2) Nonribosomal RNA should not compete for the same site.Experiments relevant to these two issues have been performed. It is the intent of the present paper to describe the results obtained and discuss their implications. The data are consistent with the existence of a specific sequence in DNA capable of complexing with homologous ribosomal RNA and not occupiable by nonribosomal RNA from the same organism.Materials and Methods.-Strain and preparation of materials: E. coli strains BB and A-155, a uracilless derivative of B were used in the present study. The methods of growth, labeling, counting, CsCl density gradient centrifugation, and the preparation of the following materials are detailed in the earlier papers;'-3 heat-denatured DNA, free of RNAase; p32 and H'-labeled 23S RNA free of "informational" RNA. The methods of assaying for RNAase activity and sensitivity of RNA-DNA complexes to nuclease degradation are the same as used in the earlier1 study.

Nucleic Acid Hybridization Studies and Deoxyribonucleic Acid Base Compositions of Anaerobic, Gram-Positive Cocci

“…Since the cistrons coding for rRNAs have changed considerably less during evolution than the rest of the genomes (15,42), DNA-rRNA hybridization studies are more useful for elucidating genetic relationships at the higher levels (i.e., genus or family level) than DNA-DNA comparisons (29). In contrast to DNA-DNA reassociation experiments, the D value between DNA and rRNA is not necessarily a relevant criterion for determining .p relationships among bacteria, since rRNA cistrons can be found in different copy numbers (29,44,45). A better criterion is the thermal stability of DNA-rRNA hybrids (9).…”

Current Topics in Microbiology and Immunology

“…An analogous situation exists with the 28S and 18S classes of r-RNA found in eukaryotic organisms. There is a loose clustering of the 23S and 16S r-RNA cistrons together with the small 5 S class of r-RNA and transfer RNA (t-RNA) (YANKOFSKY and SPIEGELMAN, 1962b;OISHI and SUEOKA, 1965;OISHI et al, 1966;CUTLER and EVANS, 1967;DUBNAU et al, 1965;SMITH et al, 1968;COLLI and OISHI, 1969;COLLI et al, 1971;DOOLITTLE and PACE, 1971). In general, the number of ribosomal cistrons is in proportion to the total amount of genetic information possessed by an organism.…”

Dna Content, Ribosomal-Rna Gene Number, and Protein Content in Soybeans

“…, 1965;Givens and Phillips, 1996;Laird and McCarthy , 1968;Phillips et a t . , 197 1 ;Phillips et al, 1974;Phillips, 1978 a, b;Ritossa and Spiegelman, 1965;Siegel et al, 1973;Yankofsky and Spiegelman, 1962. ) The redundancy in ribosomal-RNA cistrons and the broad variation in degree of redundancy have been demonstrated in higher plants.…”