Protein and Nucleic Acid Metabolism in Virus-Infected Mammalian Cells 4. THE LOCALIZATION OF METABOLIC CHANGES WITHIN SUBCELLULAR FRACTIONS OF KREBS II MOUSE-ASCITES-TUMOUR CELLS INFECTED WITH ENCEPHIALOMYOCARDITIS VlRUS* BY E. M. MARTIN AD T. S. WORK

Martin, Malec, Sved & Work (1961 b) showed that, during a single growth cycle, infection with encephalomyocarditis virus caused no changes in the total deoxyribonucleic acid, ribonucleic acid or protein of the host ascites-tumour cell. However, by the use of [6-14C]orotic acid and [14C]valine, it was shown that there were substantial changes in the rates of turnover of ribonucleic acid andprotein at different times during the cycle of virus growth. In particular, about 5 hr. after infection there was a striking increase in the rate of turnover of ribonucleic acid, and this increase coincided in time with the appearance of new virus. However, this stimulation in turnover appeared to be quantitatively greater than could be accounted for by formation of new virus ribonucleic acid. Methods have now been developed for the welldefined separation of disrupted Krebs II ascitestumour cells into nuclei, mitochondria, microsomes and cell sap (Martin, Malec, Coote & Work, 1961 a). By the use of these methods we have been able to investigate the effect of virus infection on the turnover of the ribonucleic acid and protein of the subcellular components of the host cell, and thus to localize more exactly the sites of metabolic change within the infected cell. This paper describes the result of such a study.