Replication Repair

DNA损伤导致细胞死亡或突变，两者都可能产生严重的健康后果。 大多数DNA损伤在造成伤害之前就被修复了。 经典定义的DNA修复机制是损伤的直接逆转、损伤的切除随后受损链的再合成、绕过损伤而不去除损伤的重组过程以及诱变性跨损伤合成。 第四种但特征不明显的机制已在T4噬菌体中鉴定。 某些DNA复制基因的突变会降低诱导各种DNA损伤的治疗后的存活率，但这些突变不会严重影响噬菌体的繁殖。 这个过程似乎不涉及任何经典的机制，并已被命名为？复制修复？因为它涉及到DNA复制的酶。 我们已经建立了Nossal噬菌体T4多蛋白系统，用于在体外复制DNA的两条链，我们现在正在研究受损DNA的处理，比较野生型和突变型酶。 (The DNA损伤由一个单一的、特定定位的胸腺嘧啶-胸腺嘧啶二聚体组成。） 突变的DNA结合蛋白表现出对单链DNA的亲和力降低，而突变的复制型DNA解旋酶表现出解旋酶活性降低。

Summary of Work: DNA damage produces cell death or mutation, both of which can have serious health consequences. Most DNA damage is repaired before it can cause harm. The classically defined mechanisms of DNA repair are direct reversal of the damage, excision of the damage followed by resynthesis of the damaged strand, recombinational processes that bypass the damage without removing it, and mutagenic translesion synthesis. A fourth but poorly characterized mechanism has been identified in bacteriophage T4. Mutations in certain genes of DNA replication reduce survival after treatments inducing a variety of kinds of DNA damage, but the mutations do not otherwise severely affect phage reproduction. The process appears not to involve any of the classical mechanisms and has been named ?replication repair? because it involves enzymes of DNA replication. We have set up the Nossal bacteriophage T4 multi-protein system for replicating both strands of DNA in vitro and we are now investigating the processing of damaged DNA, comparing wild-type and mutant enzymes. (The DNA damage consists of a single, specifically located thymine-thymine dimer.) A mutant DNA-binding protein exhibits reduced affinity for single-stranded DNA, while a mutant replicative DNA helicase exhibits diminished helicase activity.