Tubercidin metabolism in mouse L5178y cells in vivo and in vitro

Tubercidin (7-deazaadenosine) is a strong inhibitor of cell proliferation in mouse L5178y cells. Radioactive tubercidin is incorporated into DNA and RNA. Poly(A)-containing RNA shows the highest specific radioactivity. The amount of low molecular weight 4S and 5S RNA is diminished to some extent under the influence of the compound. Tubercidin triphosphate is a potent inhibitor of DNA-dependent DNA polymerases alpha and beta, and the DNA-dependent RNA polymerases I, II, and III, although the efficiency of its incorporation is lower than of dATP and ATP. Tubercidin triphosphate also seems to be a good substrate for the Mg2+-dependent poly(A) polymerase.