The Challenges of Cellular Senescence
HUMAN CELL Classically, a senescent cell--one that no longer divides-- will have resulted when a stem cell had undergone multiple cell divisions, which events are generally accompanied by the shortening of the telomere, a biological clock marker of cellular aging. Cellular senescence is a physiologically irreversible growth arrest process that occurs when division-prone(-competent) cells encounter oncogenic stress. In replicative senescence, the gradual loss of DNA at the end of the chromosome(the telomere), by DNA polymerases initialing RNA rather than DNA prime strand during replication and the lack of telomerases in most cells to effect repair, generate persistent DNA damage response (DDR), a vain attempt to repair DNA damage. This necessarily calls for cell division arrest. Premature senescence occurs following damage to the DNA by oxidative stress, endoplastic reticulum stress that prompts autophagy and heat shock response; through inflammation, toxins, infec...