Formation of seqence-specific telomeric DNA loops via a direct effects of psoralen-photosensitization on telomeres

摘要

DNA from HeLa cells was cleaved with Rasl and Hinf, and then purified by Bio-Gel P-2 column. Results showed that upon near-UV-irradiation, psoralen could be targeted to the repetitive sequences of telomeres. Large duplex loops with a tail were observed directly by AFM. The loop-tail junction position was assumed to be a tri- or tetra- strand DNA structure accoridng to its apparent height, corresponding structure model was proposed. The psoralen cross-linking products increased with increase of irradiation time. The expression of p53 oncogene was significantly increased.