Activation of deoxycytidine kinase during inhibition of DNA synthesis in human lymphocytes.

Deoxycytidine kinase was shown to be activated during 2-chlorodeoxyadenosine (CdA) treatment of human lymphocytes, under the conditions when the DNA synthesis is inhibited. As the increase of dCK activity was shown in crude protein extracts, without an increase in the amount of dCK protein, shown by immunostaining after SDS-PAGE, a secondary modification of the protein structure was considered. NaF treatment of cells in the concentration range of 5-20 mM gave a similar activation of dCK, suggesting a possible role of phosphatases and/or a possibility of a G-protein related phenomenon. Using the same conditions, no effect of CdA or NaF was found on the thymidine kinase activity of cell extracts. Alternatively, activation of catabolic pathways could be considered, however, the increase in dCK activity was not influenced either by the removal of 5'-nucleotidases, or by the inhibition of deaminases.