Alternative splicing (AS) generates various transcripts from a single gene and thus plays a significant role in transcriptomic diversity and proteomic complexity. Alu elements are primate-specific transposable elements (TEs) and can provide a donor or acceptor site for AS. In a study on TE-mediated AS, we recently identified a novel AluSz6-exonized ACTR8 transcript of the crab-eating monkey (Macaca fascicularis). In the present study, we sought to determine the molecular mechanism of AluSz6 exonization of the ACTR8 gene and investigate its evolutionary and functional consequences in the crab-eating monkey. We performed RT-PCR and genomic PCR to analyze AluSz6 exonization in the ACTR8 gene and the expression of the AluSz6-exonized transcript in nine primate samples, including prosimians, New world monkeys, Old world monkeys, and hominoids. AluSz6 integration was estimated to have occurred before the divergence of simians and prosimians. The Alu-exonized transcript obtained by AS was lineage-specific and expressed only in Old world monkeys and apes, and humans. This lineage-specific expression was caused by a single G duplication in AluSz6, which provides a new canonical 5′ splicing site. We further identified other alternative transcripts that were unaffected by the AluSz6 insertion. Finally, we observed that the alternative transcripts were transcribed into new isoforms with C-terminus deletion, and in silico analysis showed that these isoforms do not have a destructive function. The single G duplication in the TE sequence is the source of TE exonization and AS, and this mutation may suffer a different fate of ACTR8 gene expression during primate evolution.

中文翻译：

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ACTR8基因的单个突变与灵长类中的谱系特异性表达相关。

选择性剪接（AS）可从单个基因生成各种转录本，因此在转录组多样性和蛋白质组学复杂性中起着重要作用。Alu元素是灵长类特定的转座元素（TE），可以为AS提供供体或受体位点。在对TE介导的AS的研究中，我们最近鉴定了食蟹猴（Macaca fascicularis）的新型AluSz6编码的ACTR8转录本。在本研究中，我们试图确定ACTR8基因的AluSz6外显子化的分子机制，并研究其在食蟹猴中的进化和功能后果。我们进行了RT-PCR和基因组PCR，以分析ACTR8基因中的AluSz6外显子化和AluSz6外显子转录本在9个灵长类动物样品中的表达，包括猿猴，新世界猴，旧世界猴和类人猿。估计AluSz6整合发生在猿猴和猿猴的分歧之前。通过AS获得的Alu-exonized转录本是谱系特异性的，仅在旧世界的猴子和猿猴以及人类中表达。该谱系特异性表达是由AluSz6中的一个G重复引起的，它提供了一个新的规范5'剪接位点。我们进一步确定了不受AluSz6插入影响的其他替代转录本。最后，我们观察到替代转录物被转录为具有C末端缺失的新同工型，并且计算机分析表明这些同工型没有破坏功能。TE序列中单个G重复是TE外显和AS的来源，在灵长类动物进化过程中，此突变可能遭受ACTR8基因表达的不同命运。