RESTORATION OF MISMATCH REPAIR TO NUCLEAR EXTRACTS OF H6 COLORECTAL TUMOR-CELLS BY A HETERODIMER OF HUMAN MUTL HOMOLOGS
RESTORATION OF MISMATCH REPAIR TO NUCLEAR EXTRACTS OF H6 COLORECTAL TUMOR-CELLS BY A HETERODIMER OF HUMAN MUTL HOMOLOGS
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DOI：
10.1073/pnas.92.6.1950
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发表时间：
1995-03-14
影响因子：
11.1
通讯作者：
MODRICH, P
中科院分区：
文献类型：
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作者：
LI, GM;MODRICH, P
超变H6结直肠肿瘤细胞在链特异性错配修复中存在缺陷，并且hMLH1基因的两个等位基因都存在缺陷。我们已经从HeLa细胞中纯化出一种接近同质性的活性，这种活性与H6核提取物互补，可以恢复对一组异双工dna的修复能力，这些dna代表了8个碱基错配以及一些滑链、插入/删除错配。该活性在分离过程中表现为单一物种，并与85和110 kDa的蛋白质结合。微序列分析表明，这两个蛋白都是细菌MutL的同源物，前者对应于hMLH1产物，后者对应于hPMS2或一个密切相关基因的产物。这两种多肽的1:1摩尔化学计量和它们的流体动力学行为表明形成了异二聚体，我们将其命名为hMutL α。这些观察结果表明，人类MutL同系物家族成员之间的相互作用可能受到限制。
Hypermutable H6 colorectal tumor cells are defective in strand-specific mismatch repair and bear defects in both alleles of the hMLH1 gene. We have purified to near homogeneity an activity from HeLa cells that complements H6 nuclear extracts to restore repair proficiency on a set of heteroduplex DNAs representing the eight base-base mismatches as well as a number of slipped-strand, insertion/deletion mispairs. This activity behaves as a single species during fractionation and copurifies with proteins of 85 and 110 kDa. Microsequence analysis demonstrated both of these proteins to be homologs of bacterial MutL, with the former corresponding to the hMLH1 product and the latter to the product of hPMS2 or a closely related gene. The 1:1 molar stoichiometry of the two polypeptides and their hydrodynamic behavior indicate formation of a heterodimer, which we have designated hMutL alpha. These observations indicate that interactions between members of the family of human MutL homologs may be restricted.