INTERACTION BETWEEN DENATURED DNA, POLYRIBONUCLEOTIDES, AND RIBOSOMAL RNA: ATTEMPTS AT PREPARATIVE SEPARATION OF THE COMPLEMENTARY DNA STRANDS

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Abstract
Ribosomal RNA (rRNA) forms complexes with only one of the two complementary DNA strands of Bacillus subtilis. Similar complexes are formed when poly G substitutes for rRNA, indicating that dC-rich sequences on one of the DNA strands (most probably on the same strand along the whole genome) and G-rich sequences on rRNA are the bonding sites. Formation of such complexes permits preparative separation of the complementary DNA strands, since the mixture of denatured DNA and poly G or rRNA splits into two well-separated bands when subjected to CsCl equilibrium density-gradient centrifugation. The "heavier" band is composed of DNA strands which contain dC-rich sequences in association with a few per cent poly G or rRNA, whereas the "lighter" fraction (0.01-0.04 gm/cm3 buoyant density differential) contains the complementary strands characterized by the corresponding dG-rich sequences. Similar patterns of DNA: poly G interaction are observed for all Bacillaceae and for Escherichia coll but not necessarily for all the other organisms studied. Poly U forms complexes with both DNA strands, whereas poly I, poly C, and poly A do not interact directly with denatured DNA. The last two, however, inhibit the interaction of denatured DNA with poly G and poly U, respectively.

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