Kolesnikov N N, Elisafenko E A
Genetika. 2010 Oct;46(10):1386-91.
After the radiation of primates and rodents, the evolution of X-chromosome inactivation centers in human and mouse (XIC/Xic) followed two different directions. Human XIC followed the pathway towards transposon accumulation (the repeat proportion in the center constitutes 72%), especially LINEs, which prevail in the center. On the contrary, mouse Xic eliminated long repeats and accumulated species-specific SIN Es (the repeat proportion in the center constitutes 35%). The mechanism underlying inactivation of one of the X chromosomes in female mammals appeared on the basis of trasnsposons. The key gene of the inactivation process, XIST/Xist, similarly to other long noncoding RNA genes, like TSIX/Tsix, JPX/Jpx, and FTX/Ftx, was formed with the involvement of different transposon sequences. Furthermore, two clusters ofmicroRNA genes from inactivation center originated from L2 [1]. In mouse, one of such clusters has been preserved in the form of microRNA pseudogenes. Thus, long ncRNA genes and microRNAs appeared during the period of transposable elements expansion in this locus, 140 to 105 Myr ago, after the radiation of marsupials and placental mammal lineages.
在灵长类动物和啮齿动物分化之后，人类和小鼠的X染色体失活中心（XIC/Xic）的进化遵循了两条不同的路径。人类XIC遵循转座子积累的途径（中心区域的重复序列比例为72%），尤其是长散在核元件（LINEs），它们在中心区域占主导地位。相反，小鼠Xic消除了长重复序列，并积累了物种特异性的短散在核元件（SINEs）（中心区域的重复序列比例为35%）。雌性哺乳动物中一条X染色体失活的机制是在转座子的基础上出现的。失活过程的关键基因XIST/Xist，与其他长链非编码RNA基因类似，如TSIX/Tsix、JPX/Jpx和FTX/Ftx，是在不同转座子序列的参与下形成的。此外，来自失活中心的两簇微小RNA基因起源于L2 [1]。在小鼠中，其中一簇以微小RNA假基因的形式保留了下来。因此，长链非编码RNA基因和微小RNA是在有袋类动物和胎盘哺乳动物谱系分化之后，该位点转座元件扩张的时期，即1.4亿至1.05亿年前出现的。
