补骨脂素-UVA对端粒DNA的直接作用及其原子力显微镜研究

摘要

HeLa细胞DNA，经Rsal(1?250?U)和HinF1(1250U)内切酶酶解、Bio-gelP-2柱分离，得到端粒DNA。原子力显微镜(AFM)的直接观测结果表明在UVA照射下，补骨脂素可结合到端粒DNA的特殊位置，其光交链产物随照射时间增长而增加。与此同时，P53表达和端粒酶活性发生变化。纯化的端粒DNA片段在AFM下呈带尾的T-环结构(T-loop)。按其高度判断T-环部分为双链DNA结构，T-环与尾部交接处具有三链或四链结构特征。%DNA from HeLa cells was cleaved with Rasl and Hinf ,and thenpurified by Bio-Gel P-2 column.Results showed that upon near-UV-irradiation,psoralen coul d be targeted to the repetitive sequences of telomeres and the psoralen cross-li nking products increased with increase of irradiation time.At same time,the chan ges of the expression o f P53 oncogene and telomerase was were observed. Large duplex loops (T-loop) wit h a tail were observed directly by AFM.The loop-tail junction position was assu m ed to be a tri-or tetra- strand DNA structure according to its apparent height.