Lee Do-Yup, McMurray Cynthia T
Department of Bio and Fermentation Convergence Technology, Kookmin University, 136-702, Republic of Korea.
Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
Curr Opin Genet Dev. 2014 Jun;26:131-40. doi: 10.1016/j.gde.2014.07.003. Epub 2014 Oct 1.
Trinucleotide repeats (TNRs) expansion disorders are severe neurodegenerative and neuromuscular disorders that arise from inheriting a long tract (30-50 copies) of a trinucleotide unit within or near an expressed gene (Figure 1a). The mutation is referred to as 'trinucleotide expansion' since the number of triplet units in a mutated gene is greater than the number found in the normal gene. Expansion becomes obvious once the number of repeating units passes a critical threshold length, but what happens at the threshold to render the repeating tract unstable? Here we discuss DNA-dependent and RNA-dependent models by which a particular DNA length permits a rapid transition to an unstable state.
三核苷酸重复序列（TNRs）扩增障碍是严重的神经退行性和神经肌肉疾病，其起因是在一个表达基因内部或附近遗传了一长串（30 - 50个拷贝）的三核苷酸单元（图1a）。这种突变被称为“三核苷酸扩增”，因为突变基因中三联体单元的数量大于正常基因中的数量。一旦重复单元的数量超过临界阈值长度，扩增就会变得明显，但在阈值处会发生什么使得重复序列变得不稳定呢？在这里，我们讨论依赖DNA和依赖RNA的模型，通过这些模型，特定的DNA长度允许快速转变为不稳定状态。
