Ponte I, Vidal-Taboada J M, Suau P
Departamento de Bioquímica, Facultad de Ciencias, Universidad Autónoma de Barcelona, Spain.
Mol Biol Evol. 1998 Jun;15(6):702-8. doi: 10.1093/oxfordjournals.molbev.a025973.
Histone H1 subtypes are involved in chromatin higher-order structure. The representation of the subtypes varies greatly depending on the cellular and developmental context. We have estimated the rates of nucleotide substitution for several H1 subtypes, including mammalian and amphibian H1 degree, avian H5, and mammalian H1a-e and H1t, with the aim of finding evidence for their functional differentiation. The rates of nonsynonymous substitution differ among the subtypes by almost one order of magnitude. Such a wide variation in the degree of tolerance of amino acid substitutions is consistent with the functional differentiation of the subtypes. H1 has a characteristic three-domain structure. The rate ratios among the domains of the molecule are not systematically maintained in the different subtypes. This suggests the assumption of differentiated functions by the individual domains in chromatin structure. We have estimated the average time of divergence of H1a-e and H1t paralogs as 406 +/- 80 Myr. The lack of evidence for concerted evolution of H1a-e and H1t since long before the mammalian radiation further supports the functional differentiation of the subtypes.
组蛋白H1亚型参与染色质的高级结构。这些亚型的表现因细胞和发育环境的不同而有很大差异。我们估算了几种H1亚型的核苷酸替换率，包括哺乳动物和两栖动物的H1度、鸟类的H5以及哺乳动物的H1a - e和H1t，目的是寻找它们功能分化的证据。非同义替换率在各亚型之间相差近一个数量级。氨基酸替换耐受程度的如此广泛差异与各亚型的功能分化是一致的。H1具有特征性的三结构域结构。该分子各结构域之间的速率比在不同亚型中并非系统地保持一致。这表明染色质结构中各个结构域承担了分化的功能。我们估算出H1a - e和H1t旁系同源物的平均分歧时间为4.06 ± 0.8亿年。自哺乳动物辐射很久以前以来，H1a - e和H1t缺乏协同进化的证据，这进一步支持了各亚型的功能分化。
