EVIDENCE FOR AN EFFECT OF 5-FLUORODEOXYURIDINE ON CELLS IN THE G2 PHASE OF THE MITOTIC CYCLE

Abstract

Roots of Vicia faba were treated with 5-fluorodeoxyuridine (FUdR) for 3 hr. This compound has been used as a selective inhibitor of DNA synthesis but evidence is presented that it also arrests cells in G2 and prevents them from progressing to mitosis. Even with 10−7M solutions, inhibition is evident by 2 hr. The blockage of G2 cells occurs both in cells with a G2 of long duration (> 12 hr) and short duration (3.3 hr). The result is that any estimate of the duration of G2 in cells treated with FUdR is an underestimate. It appears that treated cells have a shorter G2 than have untreated cells but, in fact, it has been considerably extended. It is unclear why a compound that supposedly specifically inhibits DNA synthesis, by preventing the formation of thymidylic acid, should arrest cells that have already completed DNA synthesis and are in the G2 phase of the mitotic cycle.