DNA REPAIR AND SOMATIC MUTATION IN ANTIBODY VARIABLE GENES

工作总结： 可变（V）基因的体细胞超突变， 编码免疫球蛋白分子的一部分，发生的频率 是其他基因突变的一百万倍 分子 引入这些突变的机制是未知的。 该项目 三个目标。 第一个目标是研究小鼠的超突变， 来观察错配修复酶的频率和模式 突变与野生型小鼠不同。 在缺乏一种 修复蛋白PMS 2，V基因突变频率为 与野生型小鼠相似，但模式发生了改变。 数据表明 （1）串联突变是由高频率的 在单个事件期间，和（2）突变被引入到 两条DNA链，然后在过程中优先从一条链中去除 错配修复 第二个目标是确定周围的DNA序列， V基因，通过形成次级突变来激活超突变机制， 结构. 利用生物化学技术，发现了一个稳定的十字形， 含有V基因的质粒，但不含不可突变的 恒定基因，这表明这种结构可能是一个底物， 超突变第三个目标是分析V基因中的超突变， 老年人和年轻人来确定突变的频率或模式 随着年龄的变化而变化。 结果将表明是否存在与年龄相关的 超突变机制的衰退。

Summary of work: Somatic hypermutation of variable (V) genes, which encode a portion of immunoglobulin molecules, occurs at a frequency that is a million times greater than mutation in other genes. The molecular mechanism that introduces these mutations is unknown. The project has three aims. The first goal is to study hypermutation in mice deficient for mismatch repair enzymes to see if the frequency and pattern of mutation is different from wildtype mice. In mice deficient for one of the repair proteins, PMS2, the frequency of mutation in V genes was similar to wildtype mice, but the pattern was altered. The data suggest that (1) tandem mutations are generated at a high frequency by a polymerase during a single event, and (2) mutations are introduced into both strands of DNA and then preferentially removed from one strand during mismatch repair. The second goal is to identify DNA sequences around the V gene that activate the hypermutation mechanism by forming secondary structures. Using biochemical techniques, a stable cruciform was found in plasmids containing the V gene, but not in plasmids with the nonmutable constant gene, suggesting that this structure may be a substrate for hypermutation. The third goal is to analyze hypermutation in V genes from old and young humans to determine if the frequency or pattern of mutation changes with age. The results will indicate if there is an age-related decline in the hypermutation mechanism.