Evolution and function of mRNA 5'spliced leader (SL) trans-splicing

本研究的目的是了解一个重要的，但不容易理解的基因表达机制- SL反式剪接的进化和功能。 SL反式剪接是RNA剪接的一种形式，是复杂生物或细胞中大多数基因表达的重要步骤。 然而，与传统的RNA剪接不同，它从单个RNA分子中切下片段并将它们重新连接在一起，在反式剪接中，两个完全独立的RNA分子的片段连接在一起。 传统的RNA剪接在复杂的生物体中是普遍的，但是SL反式剪接虽然广泛存在，但并不是在每个群体中都发现。 分布表明SL反式剪接在进化过程中独立地出现了几次，或者已经丢失了几次。 本研究计划的目标之一是确定这些假设情景中的哪一个是正确的。这些研究将集中在包括人类在内的动物的主要分支，因为尽管人类和其他高等脊椎动物不进行SL反式剪接，但我们最近发现SL反式剪接确实发生在我们最接近的非脊椎动物脊索动物亲属被囊动物中。 我们将评估SL反式剪接在脊椎动物/脊索动物的主要群体之间的分布，以及在其他几个门中，沿着脊索动物，组成主要的动物部门称为后口动物。 这些结果将使我们能够确定SL反式剪接是否在被囊动物中出现，或者在脊椎动物中丢失。 我们也将在被囊动物中进行实验研究，以阐明脊索动物中反式剪接的遗传功能。 从这项研究的信息将提供有用的洞察基因表达机制的进化动力学和基因表达机制的进化变化对基因组进化的影响。

The goal of this research is to understand the evolution and function of an important but imperfectly-understood gene expression mechanism - SL trans-splicing. SL trans-splicing is a form of RNA splicing, which is an important step in the expression of most genes in complex organisms or cells. However, unlike conventional RNA splicing, which cuts out segments from a single RNA molecule and joins them back together, in trans-splicing segments of two entirely independent RNA molecules are joined together. Conventional RNA splicing is universal among complex organisms, but SL trans-splicing, though widespread, is not found in every group. The distribution indicates that SL trans-splicing either arose independently several times during evolution, or it has been lost several different times. One of the goals of this research program is to determine which of these hypothetical scenarios is correct. These studies will be focussed on the major branch of the animals that includes humans, because, although humans and other higher vertebrates do not carry out SL trans-splicing, we recently discovered that SL trans-splicing does occur in our closest non-vertebrate chordate relatives, the tunicates. We will assess the distribution of SL trans-splicing among the major groups of vertebrates/chordates, and also in several other phyla that, along with the chordates, make up the major animal division termed the deuterostomes. The results will enable us to determine whether SL trans-splicing arose within the tunicates, or was lost within the vertebrates. We will also carry out experimental studies in tunicates to clarify the genetic functions of trans-splicing in the chordates. The information from this research will provide useful insight into the evolutionary dynamics of gene expression mechanisms and on the impact of evolutionary change in gene expression mechanisms on the evolution of the genome.