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Deoxycytidylate Deaminase Activity of Simian Virus 40-infected Cell Cultures¹

Division of Biochemical Virology, Baylor University College of Medicine, Houston, Texas 77025

Deoxycytidine-5'-triphosphate (dCTP) stabilizes deoxycytidylate deaminase activity. Enzyme extracts prepared with buffer containing dCTP are 2 to 6 times as active as those made without dCTP. Even when extracted in the presence of dCTP, the deoxycytidylate deaminase levels vary considerably from cell cultures of different origin. Monkey and human cells exhibit about twice the activity of LM(TK^-) mouse fibroblast cells, and about 20 and 40 times the activity of confluent monolayer cultures of mouse embryo and mouse kidney cells, respectively.

An apparent stimulation of deoxycytidylate deaminase activity is observed following herpes simplex infection of LM (TK^-) cells, when dCTP is omitted from the enzyme extraction buffer. However, extracts from uninfected LM(TK^-) cells prepared with dCTP have as much activity as those from herpes simplex-infected cells. Uninfected LM(TK^-) and monkey kidney cell extracts with dCTP also exhibit as much activity as do those from vaccinia- and Simian Virus 40 (SV40)-infected cultures, respectively.

Extracts prepared with dCTP from vaccinia- or herpes simplexinfected mouse embryo and mouse kidney cultures have no more than 1.7 times the deoxycytidylate deaminase activity of uninfected cell extracts; however, thymidine kinase activity of virus-infected cell extracts is greatly increased over that of uninfected cell extracts.

Either productive-polyoma virus infection or abortive-SV40 infection of mouse kidney cells result in stimulations of both deoxycytidylate deaminase and thymidine kinase activities. These activities remain elevated in SV40-transformed mouse kidney cell cultures. Puromycin, but not 1-ß-D-arabinofuranosylcytosine, inhibits the induction of deoxycytidylate deaminase in SV40-infected mouse kidney cultures.

¹ This investigation was aided by grants from the National Science Foundation (GB 5917), the American Cancer Society (E 291), the Robert A. Welch Foundation (Q163), and by USPHS Grants CA-06656, 1-K6-AI-2352, and 5-K3-CA-25, 797.

² Postdoctoral Fellow of the Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina).

Received 1/13/67. Accepted 6/30/67.