[Synthesis of RNA and proteins with exogenous template in the DNA-directed cell-free system from Escherichia coli B. after UV-irradiation].

The RNA and protein synthesis was studied in the DNA-directed cell-free system with extracts and ribosomes of intact and ultraviolet (UV) irradiated E. coli B. The UV-doses used did not kill the cells, but produced noticeable morphological changes. DNA of bacteriophage T2 was used as a template for the RNA synthesis. All the UV-doses used cause an approximately equal decrease in the incorporation of uracil-14C into the acid-insoluble sediment in assays incubated with the extracts of the irradiated cells. The presence of ribosomes from the irradiated cells does not affect the uracil-14C incorporation. With the lower UV-doses incorporation of 14C-labelled amino acids into the acid-insoluble seciment by the irradiated cells extract decreases to the same degree as the uracil-14C incorporation. This may be the result of proportional decrease in the intensity of total RNA and m-RNA synthesis. The intensity of 14C-labelled amino-acid 14C incorporation with the ribosomes from the cells irradiated with lower UV-doses is decreased too. This testifies to a direct effect of uv on the ribosomes. With an increase in the UV-doses these effects disappear. It is supposed that the applied doses of UV-irradiation change differently the properties of the components of RNA- and protein-synthesing systens. This discrepancy becomes more noticeable with an increase in UV-dose.