Massive contractions of Myotonic Dystrophy Type 2-associated CCTG tetranucleotide repeats occur via double strand break repair with distinct requirements for helicases.
Massive contractions of Myotonic Dystrophy Type 2-associated CCTG tetranucleotide repeats occur via double strand break repair with distinct requirements for helicases.
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强直性肌营养不良 2 型相关 CCTG 四核苷酸重复序列的大量收缩是通过双链断裂修复发生的，对解旋酶有不同的要求。
DOI：
10.1101/2023.07.06.548036
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Kim,JaneC
中科院分区：
文献类型：
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作者：
Papp,David;Hernandez,LuisA;Mai,TheresaA;Haanen,TerranceJ;O'Donnell,MeghanA;Duran,ArielT;Hernandez,SophiaM;Narvanto,JenniE;Arguello,Berenice;Onwukwe,MarvinO;Kolar,Kara;Mirkin,SergeiM;Kim,JaneC
强直性肌营养不良2型（Myotonic dystrophy type 2，DM2）是由CNBP基因第一内含子中的CCTG DNA重复序列扩增引起的遗传性疾病。DM2患者中的CCTG重复的数量范围从75到11，000，但对负责重复扩增或收缩的分子机制知之甚少。我们开发了一个实验系统在酵母菌，使选择大规模的收缩（CCTG）100内的报告基因的内含子和随后的遗传分析。收缩超过80个重复单位，导致最终的重复束远低于疾病的阈值。我们发现Rad51和Rad52参与了这些大规模的收缩，这表明了一种使用同源重组的机制。Srs2解旋酶先前显示稳定CTG、CAG和CGG重复。Srs2的损失并没有显着影响在未受干扰的条件下的CCTG收缩率。相反，RecQ解旋酶Sgs1的缺失导致收缩率降低6倍，具体证据表明解旋酶活性是大规模收缩所需的。使用遗传测定来评估染色体臂丢失，我们确定与短程对照相比，CCTG和反向互补CAGG重复序列提高了染色体脆性率。总体而言，我们的研究结果表明，CCTG重复收缩的遗传控制是显着不同的致病微卫星重复序列。
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.