Negative regulation of apoptosis in yeast.

In recent years, yeast has been proven to be a useful model organism for studying programmed cell death. It not only exhibits characteristic markers of apoptotic cell death when heterologous inducers of apoptosis are expressed or when treated with apoptosis inducing drugs such as hydrogen peroxide (H(2)O(2)) or acetic acid, but contains homologues of several components of the apoptotic machinery identified in mammals, flies and nematodes, such as caspases, apoptosis inducing factor (AIF), Omi/HtrA2 and inhibitor-of-apoptosis proteins (IAPs). In this review, we focus on the role of negative regulators of apoptosis in yeasts. Bir1p is the only IAP protein in Saccharomyces cerevisiae and has long been known to play a role in cell cycle progression by acting as kinetochore and chromosomal passenger protein. Recent data established Bir1p's protective function against programmed cell death induced by H(2)O(2) treatment and in chronological ageing. Other factors that have a direct or indirect influence on intracellular levels of reactive oxygen species (ROS) and thus lead to apoptosis if they are misregulated or non-functional will be discussed.