Abstract： Telomere degradation is reported to be the initial event that triggers multiple DNA damage responses,and the nature of the event is likely to be the disclosure of concealed single-stranded 3'overhang.Exogenous telomere homolog oligonucleotide Can mimic the signal of telomere degradation in the absence of UV-induced DNA damage and enhance the DNA repair capacity of organisms,so as to defend against the damage induced by UV irradimion.The fact that telomere homolog oligonucleotides trigger SOS-like responses and cause selective apoptosis of malignantly transformed cells may provide an important clue to the prevention and treatment of photo-induced skin tumors.