CIMAR/CIIMAR, Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 177, 4050-123 Porto, Portugal.
Genomics. 2012 Feb;99(2):81-9. doi: 10.1016/j.ygeno.2011.12.001. Epub 2011 Dec 14.
Retinoid X receptors (RXR) are transcription factors with important roles in development, reproduction, homeostasis, and cell differentiation. Different types of vertebrate RXRs (α (RXRA), ß (RXRB) and γ (RXRG)) have arisen from multiple duplication events. The adaptive evolution mechanism that has preserved duplicate RXR paralogs, as well as their role in development and adaptation, is thus far unknown. In this work, we have investigated different aspects of vertebrate RXR evolution. Codon based tests of positive selection identified that RXR was under significant positive selection immediately after the whole genome duplications in vertebrates. Amino acid based rate shift analysis also revealed significant rate shifts immediately after the whole genome duplications and functional divergence between all the pairs of RXRs. However, the extant RXR genes are highly conserved, particularly the helix involved in dimerization and the DNA-binding domain, but positively selected sites can nevertheless be found in domains for RXR regulation.
视黄酸受体 X（RXR）是转录因子，在发育、生殖、内稳态和细胞分化中具有重要作用。不同类型的脊椎动物 RXR（α（RXRA）、β（RXRB）和γ（RXRG））是由多次重复事件产生的。迄今为止，保存重复 RXR 同源基因的适应进化机制及其在发育和适应中的作用尚不清楚。在这项工作中，我们研究了脊椎动物 RXR 进化的不同方面。基于密码子的正选择检验表明，在脊椎动物全基因组加倍后，RXR 受到了显著的正选择。基于氨基酸的速率转换分析也揭示了全基因组加倍后以及所有 RXR 对之间的功能分化后，存在显著的速率转换。然而，现存的 RXR 基因高度保守，特别是涉及二聚化的螺旋和 DNA 结合域，但在 RXR 调节域中仍然可以找到正选择的位点。
