Telomerase, DNA damage and apoptosis

DNA is the molecular template upon which the diversity of organisms, as well as their evolutionary stability and plasticity in response to environmental demands, is based. Every nucleotide needs to be in its proper place and, accordingly, cells have evolved a molecular machinery that ensures the precise duplication of the genome prior to cell division. Cells also possess highly refined mechanisms for repairing damaged DNA molecules. DNA can be damaged in many ways including single-strand breaks, more severe double-strand breaks, and macromolecular rearrangements including translocations and end-to-end fusions of chromosomes. These kinds of damage can be inflicted by non-specific attack of the DNA strands by oxygen free radicals, by depletion or imbalances of DNA nucleotide precursor pools, or by more specific enzymatic reactions. DNA strand breaks can be induced by a variety of chemicals and, indeed, the ability of chemicals to induce DNA damage is strongly correlated with their ability to promote cancer formation.