TELOMERES AND DNA DAMAGE. “Telomere length is highly connected with the replicative lifespan of metazoan cells. Telomeres shorten with each successive round of DNA replication until one telomere reaches a threshold of “shortness” that emits a chronic DNA damage signal that causes the cell to cease dividing and enter senescence. Mechanistically, the short telomeres are seen as chronic DNA damage by the cell, resulting in the activation of the DNA damage response, which causes a G1 cell cycle arrest.”
http://journal.frontiersin.org/article/10.3389/fgene.2013.00136/full