Vos J M, Hanawalt P C
Cell. 1987 Aug 28;50(5):789-99. doi: 10.1016/0092-8674(87)90337-0.
We have examined DNA repair in the dihydrofolate reductase (DHFR) gene in cultured human cells treated with 4'-hydroxymethyl-4,5',8-trimethylpsoralen (HMT) using a newly developed assay for interstrand DNA cross-linking in defined genomic sequences. Within 24 hr, 80% of the cross-links, but only 45% of the monoadducts, were removed from a 32 kb transcribed sequence, demonstrating that repair efficiency in an active human gene varies with the nature of the damage. HMT monoadducts were also detected in the replicated DHFR sequence at frequencies indicating little interference with replication. The existence of cross-linkable monoadduct sites in the replicated DNA implies strand continuity opposite those sites and a relatively error-free mechanism of bypass. Translesion replication could circumvent transcription blockage in a damaged gene. These findings have important implications for mechanisms of mutagenesis and DNA lesion tolerance in human cells.
我们使用一种新开发的用于确定基因组序列中链间DNA交联的检测方法，研究了用4'-羟甲基-4,5',8-三甲基补骨脂素（HMT）处理的培养人细胞中二氢叶酸还原酶（DHFR）基因的DNA修复情况。在24小时内，80%的交联，但只有45%的单加合物，从一个32kb的转录序列中被去除，这表明在一个活跃的人类基因中修复效率随损伤性质而变化。在复制的DHFR序列中也检测到HMT单加合物，其频率表明对复制几乎没有干扰。复制DNA中可交联单加合物位点的存在意味着与这些位点相对的链的连续性以及相对无错误的绕过机制。跨损伤复制可以规避受损基因中的转录阻断。这些发现对人类细胞中的诱变机制和DNA损伤耐受性具有重要意义。
