Husain I, Tomkinson A E, Burkhart W A, Moyer M B, Ramos W, Mackey Z B, Besterman J M, Chen J
Department of Cell Biology, Glaxo Research Institute, Research Triangle Park, North Carolina 27709, USA.
J Biol Chem. 1995 Apr 21;270(16):9683-90. doi: 10.1074/jbc.270.16.9683.
Mammalian cell nuclei contain three biochemically distinct DNA ligases. In the present study we have found high levels of DNA ligase I and DNA ligase III activity in bovine testes and have purified DNA ligase III to near homogeneity. The high level of DNA ligase III suggests a role for this enzyme in meiotic recombination. In assays measuring the fidelity of DNA joining, we detected no significant differences between DNA ligases II and III, whereas DNA ligase I was clearly a more faithful enzyme and was particularly sensitive to 3' mismatches. Amino acid sequences of peptides derived from DNA ligase III demonstrated that this enzyme, like DNA ligase II, is highly homologous with vaccinia DNA ligase. The absence of unambiguous differences between homologous peptides from DNA ligases II and III (10 pairs of peptides, 136 identical amino acids) indicates that these enzymes are either derived from a common precursor polypeptide or are encoded from the same gene by alternative splicing. Based on similarities in amino acid sequence and biochemical properties, we suggest that DNA ligases II and III, Drosophila DNA ligase II, and the DNA ligases encoded by the pox viruses constitute a distinct family of DNA ligases that perform specific roles in DNA repair and genetic recombination.
哺乳动物细胞核含有三种生化性质不同的DNA连接酶。在本研究中，我们发现牛睾丸中DNA连接酶I和DNA连接酶III的活性水平很高，并已将DNA连接酶III纯化至接近均一。DNA连接酶III的高含量表明该酶在减数分裂重组中起作用。在测量DNA连接保真度的实验中，我们未检测到DNA连接酶II和III之间有显著差异，而DNA连接酶I显然是一种更保真的酶，对3'错配特别敏感。从DNA连接酶III衍生的肽段的氨基酸序列表明，该酶与DNA连接酶II一样，与痘苗病毒DNA连接酶高度同源。DNA连接酶II和III的同源肽段之间没有明确差异（10对肽段，136个相同氨基酸），这表明这些酶要么源自共同的前体多肽，要么由同一基因通过可变剪接编码。基于氨基酸序列和生化性质的相似性，我们认为DNA连接酶II和III、果蝇DNA连接酶II以及痘苗病毒编码的DNA连接酶构成了一个独特的DNA连接酶家族，它们在DNA修复和基因重组中发挥特定作用。
