DNA TRIPLET REPEAT PROPERTIES AND EXPANSION

至少有七种人类遗传疾病涉及突变的三核苷酸重复 (CCG和CTG)。这些包括脆性X综合征，突变导致 密切相关的脆性部位、强直性肌营养不良、棘球肌 萎缩，亨廷顿病，脊髓-小脑性共济失调1型，以及 齿状脑-苍白球萎缩。三联体重复数 从正常人到携带者再到病患的急剧增加 个人。随着不稳定序列拷贝数的增加 后代解释了非孟德尔式的遗传特性 被称为“预期”。 这个实验室已经研究了近三年的非B DNA结构 几十年。几种类型的初步调查表明 这些和相关的简单重复序列采用了不寻常的DNA结构。 我们认为，这些非B结构和这些承受能力 复制过程中的滑移解释了由 人类遗传学家。 我们将对这十个物种进行生化、物理和遗传学研究 重组质粒、DNA聚合物和 齐聚物。我们的结论是CTG重复形成非B结构 来自2D凝胶电泳实验，化学和酶 探针分析、与核小体定位有关的EM测定，以及 DNA聚合酶在CTG三联体重复序列中的暂停位置。的作用 将探索DNA构象特征上的C甲基化。 在原核生物中发现了CTG序列的扩展和缺失 细胞；这一系统可以作为理解 与人类发病年龄和严重程度有关的扩张 遗传病。此外，三联体重复序列在遗传中的作用 我们将研究真核染色体中的重组。

At least seven human genetic disorders involve mutant trinucleotide repeats (CCG and CTG). These include fragile X syndrome, mutation resulting in a closely related fragile site, myotonic dystrophy, spino-bulbar muscular atrophy, Huntington's disease, spino-cerebellar ataxia type 1, and dentatorubral-pallidoluysian atrophy. The number of triplet repeats increases dramatically from normal individuals to carriers to afflicted individuals. This increase in copy number of the unstable sequence with subsequent generations accounts for the non-Mendelian genetic property termed "anticipation". This laboratory has investigated non-B DNA structures for almost three decades. Several types of preliminary investigations demonstrate that these and related simple repeating sequences adopt unusual DNA structures. We believe that these non-B structures and these capacities to undergo slippage during replication account for the "mutagenic mutations" found by human geneticists. We shall perform biochemical, physical, and genetic studies on all ten repeating triplet sequences in recombinant plasmids, DNA polymers, and oligomers. Our conclusions that CTG repeats form non-B structures are derived from 2D gel electrophoresis experiments, chemical and enzymatic probe analyses, EM determinations related to nucleosome positioning, and DNA polymerase pause sites in the CTG triplet repeats. The role of methylation of C on DNA conformational features will be explored. Expansion and deletion of CTG sequences has been found in procaryotic cells; this system may serve as an important model for understanding expansion which is related tot he age of onset and severity of human genetic diseases. Also, the role of triplet repeat sequences in genetic recombination in eucaryotic chromosomes will be investigated.