Although several apoptotic mediators (Yca1, Aif1, Nma111, Bir1 and Ndi1) have been identified in yeast, their networking in regulation of apoptosis is not yet fully understood. They may interact and function in a similar fashion as their mammalian counterparts, however, in contrast to mitochondrial mammalian proteins, Nma111 and Bir1 are located in the nucleus, so in yeast there might be some deviations from the mammalian model (13, 14, 71) . Nevertheless, apoptotic cell-death pathways in yeast induced by H 2 O 2 , acetic acid, hyperosmotic shock, ageing and increased mRNA stability were reported to require metacaspase Yca1, nominating them as caspasedependent pathways (13, 23, 31) . Still, deletion of Yca1 in the mRNA turnover mutant lsm1D does not attenuate mRNA decay, placing Yca1 action downstream of the signal rising from mRNA level (23) . In contrast, histone phosphorylation at Ser10, which requires prior deacetylation at Lys11, has been shown to mediate H 2 O 2 -induced apoptosis independently of Yca1 (20, 21) . Also, the activity of the major mitochondrial nuclease, Nuc1, in the celldeath pathway does not require either apoptotic mediators, Yca1 or Aif1, but is affected by H2B modifications (18) . Moreover, two PCD pathways, namely induced by defects in protein N-glycosylation and triggered by ammonia in multicellular yeast colonies, do not rely on Yca1 but on as yet unknown caspase-like activity (79, 80) .