Bcl-2 family members inhibit oxidative stress-induced programmed cell death in Saccharomyces cerevisiae

Utilization of yeast to investigate the role of lipid oxidation in cell death

The yeast Saccharomyces cerevisiae is a powerful tool to investigate several aspects of the molecular mechanisms underlying programmed cell death, namely, the events involving mitochondria. Yeast has allowed new information to be gained about crucial aspects of the interaction between proapoptotic proteins Bax and Bid and mitochondria, namely, their addressing and insertion into the mitochondrial outer membrane and their ability to induce the relocalization of cytochrome c. Going one step further, the prooxidant effect of Bax can also be studied in yeast. Bax expression induces both the accumulation of reactive oxygen species and lipid oxidation. Lipid oxidation is involved in Bax-induced cell death and may be required for optimal insertion of Bax in mitochondria. The easy modulation of lipid composition in yeast is a powerful tool to investigate this process further, and studies can be extended to other regulators of apoptosis, such as proapoptotic Bid or antiapoptotic Bcl-x(L). Also, yeast is a model for the study of other types of cell death, such as autophagy-related forms of death, for which a role of lipid oxidation has also been evidenced.

A comprehensive assessment of p53-responsive genes following adenoviral-p53 gene transfer in Bcl-2-expressing prostate cancer cells

The p53 protein can induce cell cycle arrest or apoptosis following activation in response to DNA damage. The function of p53 is largely mediated by regulating the expression of downstream target genes. Adenoviral-p53 gene transfer (Ad-p53) is currently being evaluated in clinical trials as a therapeutic intervention. Tumor response is likely to be influenced by context-dependent variables, such as expression of bcl-2. Bcl-2 is upregulated in a variety of neoplasms, and can inhibit p53-dependent apoptosis. It was therefore of interest to use a global genomic strategy to assess gene expression following Ad-p53 gene transfer and to determine if the expression of specific Ad-p53-responsive genes could be modulated in the context of bcl-2 gene deregulation. cDNA arrays were used to identify p53-responsive genes following Ad-p53 gene transfer in control and bcl-2-overexpressing PC3 prostate cancer cells. A total of 40 transcripts were significantly upregulated by Ad-p53 in both control and bcl-2-transfectant PC3 cells. Conversely, 19 transcripts were significantly repressed in both cell lines. These Ad-p53-responsive transcripts included previously identified p53 targets, known genes representing candidate p53 targets, and transcripts identified as expressed sequence tags. A subset of 15 transcripts was differentially modulated by Ad-p53 in the context of bcl-2. Some of these genes were also differentially modulated in LNCaP (wt p53) cells following DNA damage. These results document a number of potential p53 targets and mediators of therapeutically relevant genotoxic stress. The findings further suggest that bcl-2 may inhibit cell death at multiple points downstream of p53 activation.