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首页> 外文期刊>PLoS Genetics >Phylogenomics of Unusual Histone H2A Variants in Bdelloid Rotifers
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Phylogenomics of Unusual Histone H2A Variants in Bdelloid Rotifers

机译：Bdelloid轮虫中不常见的组蛋白H2A变体的系统经济学

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Rotifers of Class Bdelloidea are remarkable in having evolved for millions of years, apparently without males and meiosis. In addition, they are unusually resistant to desiccation and ionizing radiation and are able to repair hundreds of radiation-induced DNA double-strand breaks per genome with little effect on viability or reproduction. Because specific histone H2A variants are involved in DSB repair and certain meiotic processes in other eukaryotes, we investigated the histone H2A genes and proteins of two bdelloid species. Genomic libraries were built and probed to identify histone H2A genes in Adineta vaga and Philodina roseola, species representing two different bdelloid families. The expressed H2A proteins were visualized on SDS-PAGE gels and identified by tandem mass spectrometry. We find that neither the core histone H2A, present in nearly all other eukaryotes, nor the H2AX variant, a ubiquitous component of the eukaryotic DSB repair machinery, are present in bdelloid rotifers. Instead, they are replaced by unusual histone H2A variants of higher mass. In contrast, a species of rotifer belonging to the facultatively sexual, desiccation- and radiation-intolerant sister class of bdelloid rotifers, the monogononts, contains a canonical core histone H2A and appears to lack the bdelloid H2A variant genes. Applying phylogenetic tools, we demonstrate that the bdelloid-specific H2A variants arose as distinct lineages from canonical H2A separate from those leading to the H2AX and H2AZ variants. The replacement of core H2A and H2AX in bdelloid rotifers by previously uncharacterized H2A variants with extended carboxy-terminal tails is further evidence for evolutionary diversity within this class of histone H2A genes and may represent adaptation to unusual features specific to bdelloid rotifers.
机译：Bdelloidea类轮虫在进化了数百万年中表现出色，显然没有雄性和减数分裂。此外，它们异常地抗干燥和电离辐射，并且能够修复每个基因组数百个辐射诱导的DNA双链断裂，而对存活率或繁殖的影响很小。因为特定的组蛋白H2A变体参与了其他真核生物的DSB修复和某些减数分裂过程，所以我们研究了两个双倍体物种的组蛋白H2A基因和蛋白质。建立了基因组库并对其进行了探测，以识别Adineta vaga和Philodina roseola中的组蛋白H2A基因，这两个物种代表了两个不同的皮下家族。在SDS-PAGE凝胶上观察表达的H2A蛋白，并通过串联质谱法鉴定。我们发现，在几乎所有其他真核生物中都没有存在的核心组蛋白H2A，或真核DSB修复机制中无处不在的H2AX变体，都不存在于类轮虫轮虫中。相反，它们被质量更高的非常规组蛋白H2A变体所替代。相比之下，轮虫属的一类轮虫属于兼性的，干燥和辐射不耐受的姊妹类轮虫，单性腺包含一个典型的核心组蛋白H2A，并且似乎缺乏该类轮虫H2A变异基因。应用系统发育工具，我们证明了Bdelloid特异的H2A变体作为典型H2A的独特谱系出现，与导致H2AX和H2AZ变体的谱系分开。用以前未表征的H2A变体用延长的羧基末端尾部替代以前的未表征的H2A变体中的核心H2A和H2AX，这进一步证明了此类组蛋白H2A基因在进化上的多样性，并且可能代表了对刚体轮虫特有的异常特征的适应。

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