Enzymology of base excision repair in the hyperthermophilic archaeon Pyrobaculum aerophilum
Enzymology of base excision repair in the hyperthermophilic archaeon Pyrobaculum aerophilum
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DOI：
10.1074/jbc.m302397200
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发表时间：
2003-07-04
影响因子：
4.8
通讯作者：
Jiricny, J
中科院分区：
文献类型：
--
作者：
Sartori, AA;Jiricny, J
所有生物的DNA都不断地被外源和内源试剂修饰。碱基切除修复(BER)可以抵消DNA碱基的甲基化、氧化和水解性脱氨等修饰的突变威胁。这个过程是由几种DNA糖基酶中的一种酶启动的，它去除了异常的碱基，从而启动了一系列事件，包括DNA骨架的断裂，无碱的糖-磷酸残基的去除，产生的单核苷酸缺口的填补，以及剩余缺口的连接。我们有兴趣了解BER过程如何在超嗜热性生物中发挥作用，这种生物在100摄氏度左右的温度下生长，在那里这些自发反应的速度大大加快。在我们之前的研究中，我们可以证明嗜气性考古菌至少有三种尿嘧啶-DNA糖基酶，即Pa-UDGa、Pa-UDGb和Pa-MIG，它们可以通过催化胞嘧啶自发脱氨产生的尿嘧啶残基来启动BER过程。我们现在报道嗜气假单胞菌基因组还编码BER所需的剩余功能，并表明由PA-UDGb、AP内切酶IV、DNA聚合酶B2和DNA连接酶四种编码酶组成的系统可以有效地将寡核苷酸底物中的G.U错对修复为G.C对。有趣的是，DNA聚合酶的过程性钳pA-PCNA1刺激了体外修复反应的效率。
DNA of all living organisms is constantly modified by exogenous and endogenous reagents. The mutagenic threat of modifications such as methylation, oxidation, and hydrolytic deamination of DNA bases is counteracted by base excision repair (BER). This process is initiated by the action of one of several DNA glycosylases, which removes the aberrant base and thus initiates a cascade of events that involves scission of the DNA backbone, removal of the baseless sugar-phosphate residue, filling in of the resulting single nucleotide gap, and ligation of the remaining nick. We were interested to find out how the BER process functions in hyperthermophiles, organisms growing at temperatures around 100degreesC, where the rates of these spontaneous reactions are greatly accelerated. In our previous studies, we could show that the crenarchaeon Pyrobaculum aerophilum has at least three uracil-DNA glycosylases, Pa-UDGa, Pa-UDGb, and Pa-MIG, that can initiate the BER process by catalyzing the removal of uracil residues arising through the spontaneous deamination of cytosines. We now report that the genome of P. aerophilum encodes also the remaining functions necessary for BER and show that a system consisting of four P. aerophilum encoded enzymes, Pa-UDGb, AP endonuclease IV, DNA polymerase B2, and DNA ligase, can efficiently repair a G.U mispair in an oligonucleotide substrate to a G.C pair. Interestingly, the efficiency of the in vitro repair reaction was stimulated by Pa-PCNA1, the processivity clamp of DNA polymerases.