A 32-nucleotide exon-splicing enhancer regulates usage of competing 5' splice sites in a differential internal exon.
A 32-nucleotide exon-splicing enhancer regulates usage of competing 5' splice sites in a differential internal exon.
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32 核苷酸外显子剪接增强子调节差异内显子中竞争性 5 剪接位点的使用。
DOI：
10.1128/mcb.15.8.3979
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发表时间：
1995
影响因子：
5.3
通讯作者：
Berget,SM
中科院分区：
文献类型：
--
作者：
Humphrey,MB;Bryan,J;Cooper,TA;Berget,SM
大型选择性剪接内外显子在脊椎动物基因中并不常见，并且控制其使用的机制尚不清楚。在本报告中，我们检查了人类 caldesmon 基因的 1 kb 内外显子的选择性剪接，其中包含两个相距 687 个核苷酸的受调节 5 剪接位点。在通常通过利用外显子内部 5 剪接位点剪接 caldesmon RNA 的细胞系中，包含差异外显子需要位于两个竞争 5 剪接位点之间的长的富含嘌呤的序列。该元件由四个相同的 32 核苷酸富含嘌呤重复序列组成，类似于其他基因中发现的外显子剪接增强子 (ESE)。一个 32 核苷酸重复支持外显子包含，抑制末端 5 剪接位点的使用，并在依赖于外显子增强子包含的异源外显子中发挥作用，表明富含嘌呤的 caldesmon 序列可归类为 ESE。仅当存在竞争性 5 剪接位点时，才需要 ESE 来利用内部 5 剪接位点，并且当放置在末端 5 剪接位点下游时，ESE 没有效果。在缺乏内部5剪接位点的情况下，ESE激活了天然内部5剪接位点附近通常沉默的隐性5剪接位点，表明ESE刺激了上游5剪接位点选择。我们提出 caldesmon ESE 的功能是调节差异内显子内两个 5 个剪接位点之间的竞争。
Large alternatively spliced internal exons are uncommon in vertebrate genes, and the mechanisms governing their usage are unknown. In this report, we examined alternative splicing of a 1-kb internal exon from the human caldesmon gene containing two regulated 5 splice sites that are 687 nucleotides apart. In cell lines normally splicing caldesmon RNA via utilization of the exon-internal 5 splice site, inclusion of the differential exon required a long purine-rich sequence located between the two competing 5 splice sites. This element consisted of four identical 32-nucleotide purine-rich repeats that resemble exon-splicing enhancers (ESE) identified in other genes. One 32-nucleotide repeat supported exon inclusion, repressed usage of the terminal 5 splice site, and functioned in a heterologous exon dependent on exon enhancers for inclusion, indicating that the caldesmon purine-rich sequence can be classified as an ESE. The ESE was required for utilization of the internal 5 splice site only in the presence of the competing 5 splice site and had no effect when placed downstream of the terminal 5 splice site. In the absence of the internal 5 splice site, the ESE activated a normally silent cryptic 5 splice site near the natural internal 5 splice site, indicating that the ESE stimulates upstream 5 splice site selection. We propose that the caldesmon ESE functions to regulate competition between two 5 splice sites within a differential internal exon.