Kolesnikov N N, Elisafenko E A
Genetika. 2010 Oct;46(10):1379-85.
The Xist gene belongs to the class of long noncoding regulatory RNA genes which play a key role in the process of inactivation of one of the X chromosomes in females of placental mammals. Based on interspecific comparative sequence analysis performed using a set ofbioinformatic programs and approaches, the exon-intron gene structure was first described in two species, elephant and armadillo, belonging to the most primitive placental mammal groups, Afrotheria and Xenarthra. Using multiple sequence alignment of the species representing all main groups of placental mammals (12 species), consensus sequence of the ancestral gene was reconstructed. In the gene structure four evolutionary conserved regions with the identity level of 90% and the sizes of more than 100 bp were identified. Substantial contribution of transposable elements to the gene origin, as well as mosaic evolution of certain elements of the Xist locus was demonstrated. It is likely that the ancestral gene consisted often exons and was formed before the radiation of placental mammals, in the period from 140 to 105 Myr ago.
Xist基因属于长链非编码调控RNA基因类别，在胎盘哺乳动物雌性个体的一条X染色体失活过程中起关键作用。基于使用一组生物信息学程序和方法进行的种间比较序列分析，首次在属于最原始胎盘哺乳动物类群非洲兽总目和异关节总目的两个物种——大象和犰狳中描述了外显子-内含子基因结构。通过对代表胎盘哺乳动物所有主要类群的物种（12个物种）进行多序列比对，重建了祖先基因的共有序列。在基因结构中鉴定出四个进化保守区域，其同一性水平为90%，大小超过100 bp。证明了转座元件对该基因起源的重大贡献，以及Xist基因座某些元件的镶嵌进化。祖先基因可能由十个外显子组成，在1.4亿至1.05亿年前胎盘哺乳动物辐射分化之前就已形成。
