The Role of Deoxyribonucleic Acid in Ribonucleic Acid Synthesis

Abstract 1. DNA-dependent RNA polymerase has been isolated and purified from Saccharomyces cerevisiae. The yeast enzyme resembles the polymerase from Escherichia coli and other sources in its absolute requirements for a DNA primer, a divalent cation, and all four nucleoside triphosphates. 2. Yeast RNA polymerase differs fundamentally from other RNA polymerases in its marked preference for a denatured template. With a wide variety of DNA preparations, the extent of RNA synthesis is more than 10-fold greater with a denatured than with a native template. 3. In contrast to E. coli polymerase, RNA chains formed with yeast polymerase from denatured calf thymus and T2 DNA have long average chain lengths of 1500 to 2000 nucleotides. 4. The effects of yeast and E. coli polymerases on the retention of native DNA by nitrocellulose membranes, on the partitioning of DNA by polyethylene glycol-dextran, and on the rate of RNA synthesis from dAT copolymer at various temperatures have been compared. These studies suggest that the yeast enzyme has a decreased ability to cause localized denaturation of native DNA compared to the E. coli enzyme.