Laboratory of Eukaryotic Microbiology and Animal Biology, School of Biosciences and Veterinary Medicine, University of Camerino, Camerino 62032, Italy.
Laboratory of Eukaryotic Microbiology and Animal Biology, School of Biosciences and Veterinary Medicine, University of Camerino, Camerino 62032, Italy.
Gene. 2021 Jan 30;767:145186. doi: 10.1016/j.gene.2020.145186. Epub 2020 Sep 28.
In ciliates, with every sexual event the transcriptionally active genes of the sub-chromosomic somatic genome that resides in the cell macronucleus are lost. They are de novo assembled starting from 'Macronuclear Destined Sequences' that arise from the fragmentation of transcriptionally silent DNA sequences of the germline chromosomic genome enclosed in the cell micronucleus. The RNA-mediated epigenetic mechanism that drives the assembly of these sequences is subject to errors which result in the formation of chimeric genes. Studying a gene family that in Euplotes raikovi controls the synthesis of protein signal pheromones responsible for a self/not-self recognition mechanism, we identified the chimeric structure of an 851-bp macronuclear gene previously known to specify soluble and membrane-bound pheromone molecules through an intron-splicing mechanism. This chimeric gene, designated mac-er-1*, conserved the native pheromone-gene structure throughout its coding and 3' regions. Instead, its 5' region is completely unrelated to the pheromone gene structure at the level of a 360-bp sequence, which derives from the assembly with a MDS destined to compound a 2417-bp gene encoding a 696-amino acid protein with unknown function. This mac-er-1* gene characterization provides further evidence that ciliates rely on functional chimeric genes that originate in non-programmed phenomena of somatic MDS recombination to increase the species genetic variability independently of gene reshuffling phenomena of the germline genome.
在纤毛虫中，每一次有性事件都会导致位于细胞大核中的亚染色体体基因组的转录活性基因丢失。它们是从头开始组装的，从“大核定向序列”开始，这些序列来自细胞微核中封闭的生殖系染色体基因组转录沉默 DNA 序列的片段化。驱动这些序列组装的 RNA 介导的表观遗传机制容易出错，导致嵌合基因的形成。在研究一个控制蛋白信号信息素合成的基因家族时，该信息素在 Euplotes raikovi 中负责自我/非自我识别机制，我们发现了一个以前已知的 851bp 大核基因的嵌合结构，该基因通过内含子剪接机制指定可溶性和膜结合信息素分子。这个嵌合基因，命名为 mac-er-1*，在其编码和 3' 区域保留了天然信息素基因结构。相反，其 5' 区域与信息素基因结构完全无关，在 360bp 序列的水平上，它来自与 MDS 的组装，MDS 旨在组合一个编码 696 个氨基酸的未知功能的 2417bp 基因。这个 mac-er-1*基因特征提供了进一步的证据，表明纤毛虫依赖于功能性嵌合基因，这些基因起源于体细胞 MDS 重组的非程序性现象，以独立于生殖系基因组的基因重排现象来增加物种遗传多样性。
