Targeting CUG Expansions for the Treatment of Myotonic Dystrophy

描述（由申请人提供）：肌强直性营养不良1（DM 1）是一种常见的神经肌肉疾病，由肌强直蛋白激酶基因（DMPK）3 '非翻译区的多聚CTG扩增引起。这种疾病无法治愈，也没有延迟疾病进展的治疗方案。现在有强有力的证据支持多聚（CUG）RNA序列（在多聚CTG扩增转录后产生）作为DM 1的分子基础的毒性功能获得作用。poly（CUG）RNA结合并隔离重要的蛋白质，抑制它们的正常功能。这些蛋白质中最主要的是肌盲样蛋白1（MBNL 1），其作用是介导几种重要客户前mRNA的正确前mRNA剪接。由于多聚（CUG）RNA对MBNL 1的螯合，在成人中产生至少六种关键蛋白质的胎儿剪接变体，直接导致疾病症状。有相当多的遗传证据表明，MBNL 1-poly（CUG）RNA相互作用的破坏将逆转DM 1。因此，该提案的总体目标是鉴定和开发能够破坏poly（CUG）RNA-MBNL 1相互作用并逆转DM 1疾病表型的小分子。这种方法的关键是小分子必须靶向RNA，而不是MBNL 1，因为MBNL 1必须能够在细胞中正常发挥作用。poly（CUG）RNA是开发小分子结合剂的良好靶标，因为poly（CUG）形成结构化的稳定发夹，并且CUG重复序列不是细胞正常功能的一部分。因此，这种RNA序列的特异性靶向应该破坏与MBNL 1的相互作用，而不影响其他基本的细胞过程。该提案的具体目的是：1）探测MBNL蛋白对poly（CUG）RNA的结合亲和力和特异性，2）鉴定poly（CUG）RNA的小分子结合剂，3）评估在体外和强直性肌营养不良的细胞培养模型中破坏poly（CUG）RNA-MBNL 1相互作用的化合物。通过追求这些目标，我们的目标是快速验证poly（CUG）RNA作为治疗DM 1的靶点，并鉴定适合于DM 1临床前模型中药物化学优化和评价的化合物。

DESCRIPTION (provided by applicant): Mytotonic dystrophy 1 (DM1) is a prevalent neuromuscular disorder that is caused by a poly-CTG expansion in the 3'-untranslated region of the myotonic protein kinase gene (DMPK). This disease cannot be cured, and there are no treatment options that delay disease progression. There is now strong evidence supporting a toxic gain-of-function role for the poly(CUG)RNA sequences (that result upon transcription of the poly-CTG expansion) as the molecular basis for DM1. The poly(CUG)RNA binds to and sequesters important proteins, inhibiting their normal function. Chief among these proteins is muscleblind-like protein 1 (MBNL1), which acts to mediate proper pre-mRNA splicing of several important client pre-mRNAs. As a result of the sequestration of MBNL1 by poly(CUG)RNA, fetal splice variants of at least six key proteins are produced in the adult, leading directly to the disease symptoms. There is considerable genetic evidence that disruption of the MBNL1-poly(CUG)RNA interaction will reverse DM1. Thus, the overall goal of this proposal is to identify and develop small molecules capable of disrupting poly(CUG)RNA-MBNL1 interactions and reversing the DM1 disease phenotype. The key to this approach is that the small molecules must target the RNA, rather than MBNL1, because MBNL1 must be able to act normally in the cell. The poly(CUG)RNA is a good target for the development of small molecule binders because poly(CUG) forms a structured, stable hairpin and CUG repeat sequences are not part of the normal functioning of the cell. Thus, specific targeting of this RNA sequence should disrupt interactions with MBNL1 without affecting other essential cellular processes. The specific aims of the proposal are: 1) to probe the binding affinity and specificity of MBNL proteins for poly(CUG)RNA, 2) the identification of small-molecule binders of poly(CUG)RNA, and 3) the assessment of compounds that disrupt the poly(CUG)RNA-MBNL1 interaction in vitro and in cell culture models of myotonic dystrophy. By pursuing these aims, our goal is to rapidly validate poly(CUG)RNA as a target for the treatment of DM1, and to identify compounds that will be appropriate for medicinal chemistry optimization and evaluation in pre-clinical models of DM1.