An extended inhibitory context causes skipping of exon 7 of SMN2 in spinal muscular atrophy
An extended inhibitory context causes skipping of exon 7 of SMN2 in spinal muscular atrophy
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DOI：
10.1016/j.bbrc.2004.01.067
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发表时间：
2004-03-05
影响因子：
3.1
通讯作者：
Singh, RN
中科院分区：
文献类型：
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作者：
Singh, NN;Androphy, EJ;Singh, RN
SMN1和SMN2代表了人类运动神经元基因存活的两个几乎相同的拷贝。脊髓性肌萎缩症(SMA)最常见的原因是SMN1缺失，同时由于外显子7(C6U)第6位的抑制性突变导致外显子7排除，SMN1不能代偿。这个单外显子核苷酸如何调控外显子7的识别一直是人们主要感兴趣的问题。根据评分矩阵和体外分析，与SF2/ASF相关的外显子剪接增强子(ESE)的取消被认为是排除外显子7的原因。然而，最近的一份报告支持创建与hnRNP A1相关的外显子剪接沉默(ESS)作为排除外显子7的决定因素。在这里，我们表明C6U加强了一个覆盖比hnRNP Al结合位点更大序列的抑制上下文。在SMN1外显子7的第一个位置添加G残基也可以加强抑制背景，促进外显子7的跳过，尽管存在SF2/ASF结合位点。通过体内选择和一系列突变，我们证明了外显子7 5‘端延伸抑制上下文的加强是通过重叠的序列基序协同调节外显子的使用来实现的。(C)2004 Elsevier Inc.保留所有权利。
SMN1 and SMN2 represent the two nearly identical copies of the survival of motor neuron gene in humans. The most frequent cause of spinal muscular atrophy (SMA) is loss of SMN1 accompanied by the inability of SMN2 to compensate due to an inhibitory mutation at position 6 in exon 7 (C6U) that causes exon 7 exclusion. How this single exonic nucleotide regulates exon 7 recognition has been of major interest. Based on score matrices and in vitro assays, abrogation of an exonic splicing enhancer (ESE) associated with SF2/ASF has been considered as the cause of exon 7 exclusion. However, a recent report supports the creation of an exonic splicing silencer (ESS) associated with hnRNP Al as the determining factor for exon 7 exclusion. Here we show that C6U strengthens an inhibitory context that covers a larger sequence than the hnRNP Al binding site. The inhibitory context can also be strengthened by the addition of a G residue at the first position of exon 7 in SMN1, promoting exon 7 skipping despite the presence of SF2/ASF binding site. Through in vivo selection and a series of mutations we demonstrate that the strengthening of the extended inhibitory context at the 5' end of exon 7 is exercised through overlapping sequence motifs that collaborate to regulate exon usage. (C) 2004 Elsevier Inc. All rights reserved.