Thatcher T H, MacGaffey J, Bowen J, Horowitz S, Shapiro D L, Gorovsky M A
Department of Biology, University of Rochester, NY 14627.
Nucleic Acids Res. 1994 Jan 25;22(2):180-6. doi: 10.1093/nar/22.2.180.
All three genes encoding histone H3 proteins were cloned and sequenced from Tetrahymena thermophila. Two of these genes encode a major H3 protein identical to that of T. pyriformis and 87% identical to the major H3 of vertebrates. The third gene encodes hv2, a quantitatively minor replication independent (replacement) variant. The sequence of hv2 is only 85% identical to the animal replacement variant H3.3 and is the most divergent H3 replacement variant described. Phylogenetic analysis of 73 H3 protein sequences suggests that hv2, H3.3, and the plant replacement variant H3.III evolved independently, and that H3.3 is not the ancestral H3 gene, as was previously suggested (Wells, D., Bains, W., and Kedes, L. 1986, J. Mol. Evol., 23: 224-241). These results suggest it is the replication independence and not the particular protein sequence that is important in the function of H3 replacement variants.
从嗜热四膜虫中克隆并测序了编码组蛋白H3蛋白的所有三个基因。其中两个基因编码的主要H3蛋白与梨形四膜虫的相同，与脊椎动物的主要H3蛋白有87%的同一性。第三个基因编码hv2，这是一种数量上较少的不依赖复制（替代）变体。hv2的序列与动物替代变体H3.3只有85%的同一性，是所描述的最具分歧的H3替代变体。对73个H3蛋白序列的系统发育分析表明，hv2、H3.3和植物替代变体H3.III是独立进化的，并且H3.3并非如之前所认为的那样是祖先H3基因（Wells, D., Bains, W., and Kedes, L. 1986, J. Mol. Evol., 23: 224 - 241）。这些结果表明，对于H3替代变体的功能而言，重要的是不依赖复制，而非特定的蛋白质序列。
