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首页> 外文期刊>Molecular and Cellular Biology >A 32-nucleotide exon-splicing enhancer regulates usage of competing 5' splice sites in a differential internal exon.
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A 32-nucleotide exon-splicing enhancer regulates usage of competing 5' splice sites in a differential internal exon.

机译：32个核苷酸的外显子剪接增强子可调节内部差异外显子中竞争性5'剪接位点的使用。

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摘要

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.
机译：大型或选择性剪接的内部外显子在脊椎动物基因中并不常见，控制其使用的机制尚不清楚。在这份报告中，我们检查了来自人caldesmon基因的1 kb内部外显子的可变剪接，其中包含两个相距687个核苷酸的5'调控剪接位点。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在两个竞争的5'剪接位点之间有一个长的富含嘌呤的序列。该元件由四个相同的富含32个核苷酸的嘌呤重复序列组成，类似于在其他基因中鉴定的外显子剪接增强子（ESE）。一个32个核苷酸的重复序列支持外显子包被，抑制了末端5'剪接位点的使用，并在依赖于外显子增强子的异源外显子中起作用，这表明富含卡德斯顿嘌呤的序列可以归类为ESE。仅在竞争的5'拼接位点存在时才需要ESE来利用内部5'拼接位点，而当位于末端5'拼接位点的下游时，则没有作用。在没有内部5'剪接位点的情况下，ESE在自然内部5'剪接位点附近激活了一个通常沉默的隐秘5'剪接位点，表明ESE刺激了上游5'剪接位点的选择。我们建议，caldesmon ESE的功能是调节内部差异外显子中两个5'剪接位点之间的竞争。

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