Department of Public Health, University of South Carolina, Columbia, SC 29208, USA.
Department of Exercise Science, University of South Carolina, Columbia, SC 29208, USA.
DNA Repair (Amst). 2020 Dec;96:102975. doi: 10.1016/j.dnarep.2020.102975. Epub 2020 Sep 28.
Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare autosomal, dominant genetic condition characterized by many features of accelerated aging. On average, children with HGPS live to about fourteen years of age. The syndrome is commonly caused by a point mutation in the LMNA gene which normally codes for lamin A and its splice variant lamin C, components of the nuclear lamina. The LMNA mutation alters splicing, leading to production of a truncated, farnesylated form of lamin A referred to as "progerin." Progerin is also expressed at very low levels in healthy individuals and appears to play a role in normal aging. HGPS is associated with an accumulation of genomic DNA double-strand breaks (DSBs), suggesting corruption of DNA repair. In this work, we investigated the influence of progerin expression on DSB repair in the human genome at the nucleotide level. We used a model system that involves a reporter DNA substrate inserted in the genome of cultured human cells. A DSB could be induced within the substrate through exogenous expression of endonuclease I-SceI, and DSB repair events occurring via either homologous recombination (HR) or nonhomologous end-joining (NHEJ) were recoverable. Additionally, spontaneous HR events were recoverable in the absence of artificial DSB induction. We compared DSB repair and spontaneous HR in cells overexpressing progerin versus cells expressing no progerin. We report that overexpression of progerin correlated with an increase in DSB repair via NHEJ relative to HR, as well as an increased fraction of HR events occurring via gene conversion. Progerin also engendered an apparent increase in spontaneous HR events, with a highly significant shift toward gene conversion events, and an increase in DNA amplification events. Such influences of progerin on DNA transactions may impact genome stability and contribute to aging.
亨廷顿氏舞蹈症（Huntington disease，HD）是一种罕见的常染色体显性遗传疾病，其特征是许多与衰老加速相关的表现。一般来说，患有亨廷顿氏舞蹈症的儿童平均寿命约为 14 岁。该综合征通常是由 LMNA 基因突变引起的，该基因通常编码核纤层蛋白 A 和其剪接变体核纤层蛋白 C，是核纤层的组成部分。LMNA 突变改变了剪接，导致产生一种截短的、法呢化的核纤层蛋白 A 形式，称为“progerin”。Progerin 也在健康个体中低水平表达，似乎在正常衰老中发挥作用。亨廷顿氏舞蹈症与基因组 DNA 双链断裂（DSBs）的积累有关，提示 DNA 修复受损。在这项工作中，我们研究了 progerin 表达对人类基因组核苷酸水平 DSB 修复的影响。我们使用了一种涉及培养的人类细胞基因组中插入报告 DNA 底物的模型系统。通过外源性表达内切酶 I-SceI，可以在底物中诱导 DSB，并且可以通过同源重组（HR）或非同源末端连接（NHEJ）回收发生的 DSB 修复事件。此外，在没有人工 DSB 诱导的情况下，也可以回收自发的 HR 事件。我们比较了过表达 progerin 的细胞与不表达 progerin 的细胞中的 DSB 修复和自发的 HR。我们报告说，与 HR 相比，progerin 的过表达与通过 NHEJ 修复 DSB 的增加相关，以及通过基因转换发生的 HR 事件的比例增加。Progerin 还导致自发的 HR 事件明显增加，具有高度显著的基因转换事件转移，并增加了 DNA 扩增事件。Progerin 对 DNA 交易的这种影响可能会影响基因组稳定性并导致衰老。
