Messenger-RNA attachment to active ribosomes.

16 In a current experiment, we have found that a protein fraction isolated from the 105,000 X g supernatant can catalyze a similar RNA synthesis in the presence of four nucleoside triphosphates and the E. coli DNA prepared by the method of Marmur (J. Mol. Biol., 3, 208, 1961). In this system also, the addition of salmine enhances the initial rate of the synthesis and prevents the degradation of the product. The rate is about comparable to that of the crude system. However the reaction practically ceases after ten minutes even if the nucleoside triphosphates are further added at 10-min intervals. The ratio of the synthesized RNA to the DNA added is around 0.5. The result might be explained by assuming a factor necessary for the liberation of the synthesized RNA from the DNA. In the crude system, the RNA would be continuously liberated from DNA in the presence of the "factor;" in the "purified" system, the RNA would not be liberated because of the absence of the "factor." 17 Mandell, J. D., and A. D. Hershey, Anal. Biochem., 1, 66 (1960). 18 Philipson, L., J. Gen. Physiol., 44, 899 (1961 ). 19 Britten, R. J., and R. B. Roberts, Science, 131, 32 (1960). 20 Ishihama, A., unpublished experiment (1961).