Death and more: DNA damage response pathways in the nematode C. elegans.
Genotoxic stress is a threat to our cells' genome integrity. Failure to repair DNA lesions properly after the induction of cell proliferation arrest can lead to mutations or large-scale genomic instability. Because such changes may have tumorigenic potential, damaged cells are often eliminated via apoptosis. Loss of this apoptotic response is actually one of the hallmarks of cancer. Towards the effort to elucidate the DNA damage-induced signaling steps leading to these biological events, an easily accessible model system is required, where the acquired knowledge can reveal the mechanisms underlying more complex organisms. Accumulating evidence coming from studies in Caenorhabditis elegans point to its usefulness as such. In the worm's germline, DNA damage can induce both cell cycle arrest and apoptosis, two responses that are spatially separated. The latter is a tightly controlled process that is genetically indistinguishable from developmental programmed cell death. Upstream of the central death machinery, components of the DNA damage signaling cascade lie and act either as sensors of the lesion or as transducers of the initial signal detected. This review summarizes the findings of several studies that specify the elements of the DNA damage-induced responses, as components of the cell cycle control machinery, the repairing process or the apoptotic outcome. The validity of C. elegans as a tool to further dissect the complex signaling network of these responses and the high potential for it to reveal important links to cancer and other genetic abnormalities are addressed.