PDF(Pubmed)
Abstract：
BACKGROUND: Nuclear introns in Euglenida have been understudied. This study aimed to investigate nuclear introns in Euglenida by identifying a large number of introns in Euglena gracilis (E. gracilis), including cis-spliced conventional and nonconventional introns, as well as trans-spliced outrons. We also examined the sequence characteristics of these introns.
RESULTS: A total of 28,337 introns and 11,921 outrons were identified. Conventional and nonconventional introns have distinct splice site features; the former harbour canonical GT/C-AG splice sites, whereas the latter are capable of forming structured motifs with their terminal sequences. We observed that short introns had a preference for canonical GT-AG introns. Notably, conventional introns and outrons in E. gracilis exhibited a distinct cytidine-rich polypyrimidine tract, in contrast to the thymidine-rich tracts observed in other organisms. Furthermore, the SL-RNAs in E. gracilis, as well as in other trans-splicing species, can form a recently discovered motif called the extended U6/5\' ss duplex with the respective U6s. We also describe a novel type of alternative splicing pattern in E. gracilis. The tandem repeat sequences of introns in this protist were determined, and their contents were comparable to those in humans.
CONCLUSIONS: Our findings highlight the unique features of E. gracilis introns and provide insights into the splicing mechanism of these introns, as well as the genomics and evolution of Euglenida.
RESULTS: A total of 28,337 introns and 11,921 outrons were identified. Conventional and nonconventional introns have distinct splice site features; the former harbour canonical GT/C-AG splice sites, whereas the latter are capable of forming structured motifs with their terminal sequences. We observed that short introns had a preference for canonical GT-AG introns. Notably, conventional introns and outrons in E. gracilis exhibited a distinct cytidine-rich polypyrimidine tract, in contrast to the thymidine-rich tracts observed in other organisms. Furthermore, the SL-RNAs in E. gracilis, as well as in other trans-splicing species, can form a recently discovered motif called the extended U6/5\' ss duplex with the respective U6s. We also describe a novel type of alternative splicing pattern in E. gracilis. The tandem repeat sequences of introns in this protist were determined, and their contents were comparable to those in humans.
CONCLUSIONS: Our findings highlight the unique features of E. gracilis introns and provide insights into the splicing mechanism of these introns, as well as the genomics and evolution of Euglenida.
摘要：
背景：对Euglenida中核内含子的研究不足。本研究旨在通过识别Euglenagracilis中的大量内含子来研究Euglenida中的核内含子（E.gracilis),包括顺式剪接的常规和非常规内含子，以及交叉剪接的外突。我们还检查了这些内含子的序列特征。
结果：共鉴定出28,337个内含子和11,921个外端。常规和非常规内含子具有不同的剪接位点特征；前者是典型的GT/C-AG剪接位点，而后者能够与其末端序列形成结构化基序。我们观察到短内含子对规范的GT-AG内含子具有偏好。值得注意的是,普通E.gracilis中的常规内含子和反离子表现出明显的富含胞苷的聚嘧啶束，与在其他生物体中观察到的富含胸苷的区域相反。此外，E.gracilis中的SL-RNA，以及其他反式剪接物种，可以与相应的U6形成一个最近发现的主题，称为扩展的U6/5\'ss双工。我们还描述了一种新型的可变剪接模式。确定了该原生生物中内含子的串联重复序列，它们的含量与人类相当。
结论：我们的发现突出了E.gracilis内含子的独特特征，并提供了对这些内含子剪接机制的见解，以及Euglenida的基因组学和进化。
结果：共鉴定出28,337个内含子和11,921个外端。常规和非常规内含子具有不同的剪接位点特征；前者是典型的GT/C-AG剪接位点，而后者能够与其末端序列形成结构化基序。我们观察到短内含子对规范的GT-AG内含子具有偏好。值得注意的是,普通E.gracilis中的常规内含子和反离子表现出明显的富含胞苷的聚嘧啶束，与在其他生物体中观察到的富含胸苷的区域相反。此外，E.gracilis中的SL-RNA，以及其他反式剪接物种，可以与相应的U6形成一个最近发现的主题，称为扩展的U6/5\'ss双工。我们还描述了一种新型的可变剪接模式。确定了该原生生物中内含子的串联重复序列，它们的含量与人类相当。
结论：我们的发现突出了E.gracilis内含子的独特特征，并提供了对这些内含子剪接机制的见解，以及Euglenida的基因组学和进化。
