Bernhard D, Schlegel M
Universität Leipzig, Institut für Zoologie, Spezielle Zoologie, Germany.
J Mol Evol. 1998 Mar;46(3):344-54. doi: 10.1007/pl00006311.
The histones H4 are known as highly conserved proteins. However, in ciliates a high degree of variation was found compared both to other eukaryotes and between the ciliate species. To date, only H4 histones of species belonging to two distantly related classes have been investigated. In order to obtain more detailed information on histone H4 variation in ciliates we undertook a comprehensive sequence analysis of PCR-amplified internal H4 fragments from 12 species belonging to seven out of the nine currently recognized ciliate classes. In addition, we used PCR primers to amplify longer fragments of H3 and H4 genes including the intergenic region. The encoded amino acid sequences reveal a high number of differences when compared with those of other eukaryotes and the ciliate species investigated. Furthermore, in some species H4 gene variants were detected, which result in amino acid differences. The greatest number of substitutions and insertions found was in the amino terminal region of the H4 histones. However, all sequences possess a conserved region corresponding to those of all other eukaryotic H4 histones. The histone gene variations were used to reconstruct phylogenetic relationships. The tree from our data matches perfectly with the ribosomal RNA data: The heterotrichs, which were considered as a late branching lineage, diverge at the base of the ciliate tree and groups formerly thought to represent ancestral lineages now appear as highly derived ciliates.
组蛋白H4是众所周知的高度保守的蛋白质。然而，与其他真核生物相比，在纤毛虫中发现了高度的变异性，并且在不同的纤毛虫物种之间也存在高度变异性。迄今为止，仅对属于两个远缘类别的物种的H4组蛋白进行了研究。为了获得关于纤毛虫中组蛋白H4变异的更详细信息，我们对来自目前公认的九个纤毛虫类别中的七个类别中的12个物种的PCR扩增的内部H4片段进行了全面的序列分析。此外，我们使用PCR引物扩增包括基因间隔区在内的H3和H4基因的更长片段。与其他真核生物和所研究的纤毛虫物种的氨基酸序列相比，编码的氨基酸序列显示出大量差异。此外，在一些物种中检测到H4基因变体，这导致了氨基酸差异。发现的替换和插入数量最多的是在H4组蛋白的氨基末端区域。然而，所有序列都具有与所有其他真核生物H4组蛋白相对应的保守区域。组蛋白基因变异被用于重建系统发育关系。我们数据构建的树与核糖体RNA数据完美匹配：被认为是晚期分支谱系的异毛类在纤毛虫树的基部发散，而以前被认为代表祖先谱系的类群现在显示为高度进化的纤毛虫。
