Dipartimento di Biologia, Università degli Studi di Padova, Italy.
Dev Genes Evol. 2011 Mar;220(11-12):329-36. doi: 10.1007/s00427-011-0351-y. Epub 2011 Feb 18.
In some animals, mRNA may be modified after transcription by the addition of a 5' spliced leader sequence. This is known as spliced leader (SL) trans-splicing, and is of uncertain function and evolutionary origin. Here, we report the identification of SL trans-splicing in the colonial ascidian Botryllus schlosseri. Combining our own expressed sequence tag (EST) data with additional data from GenBank, we identify the dominant spliced leader sequence and show it to be similar to that of other ascidians and to that of Oikopleura dioica, a basally diverging tunicate. Gene Ontology analysis of B. schlosseri ESTs with and without a 5' spliced leader shows that genes encoding ribosomal proteins tend not to be trans-spliced, a character shared with the ascidian Ciona intestinalis. We also examine individual cases of genes that produce mRNAs that are SL trans-spliced in B. schlosseri but not in C. intestinalis. We conclude that SL trans-splicing evolved early in the tunicate lineage and shows stability over considerable evolutionary time. However, SL trans-splicing may be gained or lost in individual genes.
在某些动物中，mRNA 在转录后可能会通过添加 5'拼接先导序列进行修饰。这被称为拼接先导（SL）反式拼接，其功能和进化起源尚不确定。在这里，我们报告了在群体海鞘 Botryllus schlosseri 中发现的 SL 反式拼接。我们结合自己的表达序列标签（EST）数据和 GenBank 中的其他数据，确定了主要的拼接先导序列，并表明它与其他海鞘以及与基础分化的被囊动物 Oikopleura dioica 的序列相似。具有和不具有 5'拼接先导的 B. schlosseri EST 的基因本体论分析表明，编码核糖体蛋白的基因往往不会进行反式拼接，这一特征与海鞘 Ciona intestinalis 共享。我们还检查了在 B. schlosseri 中进行 SL 反式拼接但在 C. intestinalis 中不进行的个别基因的情况。我们的结论是，SL 反式拼接在被囊动物谱系中进化较早，并在相当长的进化时间内保持稳定。然而，SL 反式拼接可能在个别基因中获得或丢失。
