Kunkel T A, Gopinathan K P, Dube D K, Snow E T, Loeb L A
Proc Natl Acad Sci U S A. 1986 Mar;83(6):1867-71. doi: 10.1073/pnas.83.6.1867.
To assess the involvement of terminal transferase in generating immunoglobulin diversity, the mutagenic potential of this enzyme has been measured. The frequency of single base substitutions during copying of phi X174 DNA by DNA polymerase beta is increased by, at most, 3-fold upon the addition of terminal transferase. However, terminal transferase is highly mutagenic, either alone or with DNA polymerase beta, in a forward mutation assay using M13mp2 DNA. The frequency of complex mutants, as determined by DNA sequence, is increased by greater than 100-fold. These mutants involve the deletion of a variable number of bases initially present in the template sequence and the addition of a sequence of nucleotides rich in guanine residues. Analysis of these mutants suggests an antibody diversity model implicating terminal transferase in the imprecise linkage of variable, joining, and diversity segments during the formation of functional immunoglobulin genes.
为评估末端转移酶在产生免疫球蛋白多样性中的作用，已对该酶的诱变潜力进行了测定。在DNA聚合酶β复制phi X174 DNA过程中，单碱基替换的频率在添加末端转移酶后最多增加3倍。然而，在使用M13mp2 DNA的正向突变试验中，末端转移酶单独或与DNA聚合酶β一起时具有高度诱变性。根据DNA序列确定，复杂突变体的频率增加了100倍以上。这些突变体涉及模板序列中最初存在的可变数量碱基的缺失以及富含鸟嘌呤残基的核苷酸序列的添加。对这些突变体的分析提示了一种抗体多样性模型，该模型认为末端转移酶在功能性免疫球蛋白基因形成过程中可变区、连接区和多样性区的不精确连接中起作用。
