METHIONAL, A CELLULAR METABOLITE, INDUCES APOPTOSIS PREFERENTIALLY ING2 M-SYNCHRONIZED BAF3 MURINE LYMPHOID-CELLS/

We have previously shown that methional, derived from 4-methylthio-2-o xobutanoate, is a cellular mediator of apoptosis in BAF(3) b(0) murine lymphoid cells, which are dependent on IL3 for their growth in cultur e. When cells synchronized in S phase by double thymidine block were t reated with methional immediately after thymidine withdrawal, methiona l was unable to induce DNA-strand breaks, whereas it inhibited the pro gression of cells from 3 to G2/M phases, This inhibition of cell cycle progression was associated with a 53% decrease in DNA synthesis. In c ontrast, when BAF(3) b(0) cells were synchronized in G2/M phase using SK&F 96365, and treated with methional immediately after drug removal, methional induced DNA-strand breaks in 49% of cells in 4 h, compared to 12% in controls, As contact time increased from 4 to 8 h, DNA-stran d breaks increased to 94% in methional-treated cells compared to 11% i n controls, These observations on G2/M-synchronized cells are differen t from those seen in BAF(3)b(0) cells in G1 phase, 3 h after their rel ease from the G2/M block, in that there was no decrease in size of the G1 population even after an additional 4 h incubation in the presence of methional These results, taken together, provide a rational basis for using combinations of methional and G2/M blockers as inducers of D NA-strand breaks and apoptosis in murine lymphoid cells, (C) 1998 Wile y-Liss, Inc.