THE CYTOSTATIC ACTIVITY OF 5-(1-AZIDOVINYL)-2'-DEOXYURIDINE (AZVDU) AGAINST HERPES-SIMPLEX VIRUS THYMIDINE KINASE GENE-TRANSFECTED FM3A CELLS IS DUE TO INHIBITION OF THYMIDYLATE SYNTHASE AND ENHANCED BY UV-LIGHT (LAMBDA=254 NM) EXPOSURE

5-(1-Azidovinyl)-2'-deoxyuridine (AzVDU) and a series of 5-[1-azido-2- halogenoethyl]-derivatives of beta-D-arabinofuranosyluracil (AU) prove d markedly inhibitory to the replication of herpes simplex virus type 1 (HSV-1) and varicella tester virus (VZV), but not thymidine kinase ( TK)-deficient HSV-1 and VZV strains, None of the compounds were cytost atic, However, AzVDU, but not the 5-[1-azido-2-halogenoethyl]-AU deriv atives became highly cytostatic against HSV-1 and HSV-2 TK gene-transf ected FM3A tumor cells. The molecular target for the cytostatic effect of AzVDU proved to be thymidylate synthase, Short exposure of AzVDU-t reated FM3A TK-/HSV-1 TK+ cells to irradiation at lambda = 254 nm enha nced the cytostatic activity of AzVDU by 5-fold.