Massive contractions of myotonic dystrophy type 2-associated CCTG tetranucleotide repeats occur via double-strand break repair with distinct requirements for DNA helicases
Massive contractions of myotonic dystrophy type 2-associated CCTG tetranucleotide repeats occur via double-strand break repair with distinct requirements for DNA helicases
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DOI：
10.1093/g3journal/jkad257
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发表时间：
2023-11-10
影响因子：
2.6
通讯作者：
Kim，Jane C.
中科院分区：
文献类型：
--
作者：
Papp，David;Hernandez，Luis A.;Kim，Jane C.
强直性肌营养不良2型（DM2）是一种由CNBP第一个内含子中CCTG DNA重复扩增引起的遗传性疾病。 DM2 患者中 CCTG 重复的数量范围为 75 至 11,000，但对于重复扩张或收缩的分子机制知之甚少。我们在酿酒酵母中开发了一个实验系统，能够选择报告基因内含子内的 (CCTG)100 的大规模收缩并进行后续的遗传分析。收缩超过 80 个重复单位，导致最终的重复束远低于疾病阈值。我们发现 Rad51 和 Rad52 参与了这些大规模收缩，表明使用同源重组的机制。先前已证明 Srs2 解旋酶可稳定 CTG、CAG 和 CGG 重复序列。在不受干扰的条件下，Srs2 的丢失并没有显着影响 CCTG 收缩率。相比之下，RecQ 解旋酶 Sgs1 的丢失导致收缩率下降 6 倍，有具体证据表明解旋酶活性是大规模收缩所必需的。使用遗传测定来评估染色体臂丢失，我们确定与短轨对照相比，CCTG 和反向互补 CAGG 重复会提高染色体脆性率。总体而言，我们的结果表明，CCTG 重复收缩的遗传控制在致病微卫星重复序列中显着不同。
Myotonic dystrophy type 2 (DM2) is a genetic disease caused by expanded CCTG DNA repeats in the first intron ofCNBP. The number of CCTG repeats in DM2 patients ranges from 75 to 11,000, yet little is known about the molecular mechanisms responsible for repeat expansions or contractions. We developed an experimental system inSaccharomyces cerevisiaethat enables the selection of large-scale contractions of (CCTG)100within the intron of a reporter gene and subsequent genetic analysis. Contractions exceeded 80 repeat units, causing the final repetitive tract to be well below the threshold for disease. We found that Rad51 and Rad52 are involved in these massive contractions, indicating a mechanism that uses homologous recombination. Srs2 helicase was shown previously to stabilize CTG, CAG, and CGG repeats. Loss of Srs2 did not significantly affect CCTG contraction rates in unperturbed conditions. In contrast, loss of the RecQ helicase Sgs1 resulted in a 6-fold decrease in contraction rate with specific evidence that helicase activity is required for large-scale contractions. Using a genetic assay to evaluate chromosome arm loss, we determined that CCTG and reverse complementary CAGG repeats elevate the rate of chromosomal fragility compared to a short-track control. Overall, our results demonstrate that the genetic control of CCTG repeat contractions is notably distinct among disease-causing microsatellite repeat sequences.