Dramatic diversity of ciliate histone H4 genes revealed by comparisons of patterns of substitutions and paralog divergences among eukaryotes
Dramatic diversity of ciliate histone H4 genes revealed by comparisons of patterns of substitutions and paralog divergences among eukaryotes
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DOI：
10.1093/molbev/msh048
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发表时间：
2004-03-01
影响因子：
10.7
通讯作者：
Muse, SV
中科院分区：
文献类型：
--
作者：
Katz, LA;Bornstein, JG;Muse, SV
不同组蛋白H4氨基酸序列在纤毛虫谱系内部和之间的积累挑战了这一重要真核蛋白进化的传统观点。我们分析了13种纤毛虫的组蛋白H4序列，并将这些数据与真核进化枝的序列进行了比较。与大多数其他真核生物中这种蛋白质的高度保守性形成鲜明对比的是，纤毛虫组蛋白H4s在多达46%的氨基酸上彼此不同。同样令人吃惊的是，我们发现在纤毛虫基因组中，组蛋白H4的相似物存在高达25%的氨基酸差异，而在其他真核生物中，相似物具有相同或几乎相同的氨基酸序列。此外，在具有高度加工的大核基因组的谱系中发现了纤毛虫中最具差异性的H4蛋白。我们的分析表明，纤毛虫基因组的双重性质——每个细胞中存在“种系”微核和“体细胞”宏核——允许纤毛虫组蛋白基因通过改变功能限制或使组蛋白H4蛋白的适应性进化或两者兼有而发生巨大变化。
The accumulation of divergent histone H4 amino acid sequences within and between ciliate lineages challenges traditional views of the evolution of this essential eukaryotic protein. We analyzed histone H4 sequences from 13 species of ciliates and compared these data with sequences from well-sampled eukaryotic clades. Ciliate histone H4s differ from one another at as many as 46% of their amino acids, in contrast with the highly conserved character of this protein in most other eukaryotes. Equally striking, we find paralogs of histone H4 within ciliate genomes that differ by up to 25% of their amino acids, whereas paralogs in other eukaryotes share identical or,nearly identical amino acid sequences. Moreover, the most divergent H4 proteins within ciliates are found in the lineages with highly processed macronuclear genomes. Our analyses demonstrate that the dual nature of ciliate genomes-the presence of a "germline" micronucleus and a "somatic" macronucleus within each cell-allowed the dramatic variation in ciliate histone genes by altering functional constraints or enabling adaptive evolution of the histone H4 protein, or both.