Promotes programmed cell death. Its role in programmed cell death may be in conjunction with cell cycle regulatory factor efl-1 and the synthetic multivulva class B proteins dpl-1 and lin-35, and is independent of the ced-1, ced-8 and ced-9 pathways. Enhances the cell death defect of ced-3(n2427) mutants. Double knockout with the synthetic multivulva (synMuv) class B proteins lin-9, lin-15B, lin-35 or lin-54 results in 100% lethality during the L1 stage of larval development. Double knockout with the synMuv class B protein lin-53 results in slow larval growth.