Molecular mechanisms responsible for aberrant splicing of SERCA1 in myotonic dystrophy type 1
Molecular mechanisms responsible for aberrant splicing of SERCA1 in myotonic dystrophy type 1
复制标题
DOI：
10.1093/hmg/ddm239
复制
发表时间：
2007-12-01
影响因子：
3.5
通讯作者：
Imaizumi, Kazunori
中科院分区：
文献类型：
--
作者：
Hino, Shin-ichiro;Kondo, Shinichi;Imaizumi, Kazunori
强直性肌营养不良1型（DM 1）是一种常染色体显性遗传神经肌肉疾病，与强直性肌营养不良蛋白激酶（DMPK）基因3 '非翻译区CTG三核苷酸重复序列扩增相关。RNA功能获得假说提出突变的DMPK mRNA改变了选择性剪接调节子的功能和定位，这对正常的RNA加工至关重要。以前，我们发现选择性剪接变异体的肌浆网/内质网Ca 2 +-ATP酶1（SERCA 1），其中排除外显子22，在DM 1患者的骨骼肌。在本研究中，我们分析了SERCA 1剪接失调的分子机制。SERCA 1外显子22的下游包括5个可能潜在地用作肌盲样1（MBNL 1）结合基序的“YGCU（U/G）Y”基序。外显子捕获实验表明，MBNL 1作用于“YGCU（U/G）Y”基序，并正调控外显子22剪接。在内含子22的5个MBNL 1基序中，第二和第三个位点对外显子22剪接的调控很重要，但其他3个结合位点不是必需的。DMPK mRNA的CUG重复扩增的过表达导致SERCA 1的外显子22被排除。这些结果表明，MBNL 1的螯合到DMPK mRNA的CUG重复扩增可能会导致SERCA 1外显子22的排斥，这种异常剪接形式的SERCA 1的表达可能会影响DM患者肌浆网Ca 2+浓度的调节。
Myotonic dystrophy type 1 (DM1) is an autosomal dominant neuromuscular disorder associated with an expansion of CTG trinucleotide repeats in the 3'-untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. The RNA gain-of-function hypothesis proposes that mutant DMPK mRNA alters the function and localization of alternative splicing regulators, which are critical for normal RNA processing. Previously, we found alternative splicing variants of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 1 (SERCA1), which excluded exon 22, in skeletal muscle of DM1 patients. In the present study, we analyzed the molecular mechanisms responsible for the splicing dysregulation of SERCA1. Five 'YGCU(U/G)Y' motifs that could potentially serve as Muscleblind-like 1, (MBNL1)-binding motifs, are included downstream from the SERCA1 exon 22. Exon trapping experiments showed that MBNL1 acts on the 'YGCU(U/G) Y' motif, and positively regulates exon 22 splicing. Of the five MBNL1 motifs in intron 22, the second and third sites were important for regulation of exon 22 splicing, but the other three binding sites were not required. Overexpression of the CUG repeat expansion of DMPK mRNA resulted in exclusion of exon 22 of SERCA1. These results suggest that sequestration of MBNL1 into the CUG repeat expansion of DMPK mRNA could cause the exclusion of SERCA1 exon 22, and the expression of this aberrant splicing form of SERCA1 could affect the regulation of Ca2+ concentration of sarcoplasmic reticulum in DM patients.