Vorobyov Eugene, Horst Jürgen
Institut für Humangenetik, UKM, Vesaliusweg 12-14, D-48149, Münster, Germany.
J Mol Evol. 2006 Aug;63(2):153-64. doi: 10.1007/s00239-005-0163-7. Epub 2006 Jul 7.
Pax genes encode transcription factors governing the determination of different cell types and even organs in the development of multicellular animals. Pax proteins are characterized by the presence of three evolutionarily conserved elements: two DNA-binding domains, the paired domain (PD) and paired-type homeodomain (PtHD), and the short octopeptide sequence (OP) located between PD and PtHD. PD is the defining feature of this class of genes, while OP and/or PtHD may be divergent or absent in some members of the family. Phylogenetic analyses of the PD and PtHD sequences do not distinguish which particular type of the extant Pax genes more resembles the ancestral type. Here we present evidence for the existence of a fourth evolutionarily conserved domain in the Pax proteins, the paired-type homeodomain tail (PHT). Our data also imply that the hypothetical proto-Pax protein most probably exhibited a complex structure, PD-OP-PtHD-PHT, which has been retained in the extant proteins Pax3/7 of the ascidia and lancelet, and Pax7 of the vertebrates. Finally, based on structural considerations, a scenario for the evolutionary emergence of the proto-Pax gene is proposed.
Pax基因编码转录因子，这些转录因子在多细胞动物的发育过程中决定不同的细胞类型甚至器官。Pax蛋白的特征是存在三个进化上保守的元件：两个DNA结合结构域，即配对结构域（PD）和配对型同源结构域（PtHD），以及位于PD和PtHD之间的短八肽序列（OP）。PD是这类基因的决定性特征，而OP和/或PtHD在该家族的一些成员中可能有所不同或不存在。对PD和PtHD序列的系统发育分析无法区分现存的哪种特定类型的Pax基因更类似于祖先类型。在此，我们提供证据证明Pax蛋白中存在第四个进化上保守的结构域，即配对型同源结构域尾部（PHT）。我们的数据还表明，假设的原始Pax蛋白很可能具有复杂的结构，即PD-OP-PtHD-PHT，这种结构在现存的海鞘和文昌鱼的Pax3/7蛋白以及脊椎动物的Pax7蛋白中得以保留。最后，基于结构上的考虑，提出了原始Pax基因进化出现的一种设想。
