School of Life Sciences, University of Glasgow, Glasgow, United Kingdom.
Ann N Y Acad Sci. 2012 Oct;1269:7-15. doi: 10.1111/j.1749-6632.2012.06684.x.
Evolution probably invented the β-thymosin domain in a single-celled close relative of multicellular animals. Expansion from single genes to the small family of monomeric β-thymosins of present-day vertebrates may have started with a very ancient duplication, before the rounds of whole-genome duplications. In land vertebrates and fish, this family consists of the descendants of five genes of their jawed vertebrate common ancestor. Identifying this common ancestry depends on the genes possessing conserved sets of flanking sequences, as the relationships are not recognizable from amino-acid sequences. One of these genes has given rise both to a group of fish β-thymosins and to a hitherto unrecognized group of β-thymosins of birds and reptiles. The resulting classification may prove useful in relation to the β-thymosins of model organisms, such as the zebrafish, and for identifying important noncoding sequence elements, exemplified here by a conserved sequence in the 3'untranslated region of transcripts from the β4 subfamily.
β-胸腺素结构域可能是由多细胞动物的单细胞近亲进化而来的。从单个基因扩展到现今脊椎动物的单体β-胸腺素小家族，可能始于非常古老的复制，发生在全基因组复制之前。在陆栖脊椎动物和鱼类中，该家族由其有颌脊椎动物共同祖先的五个基因的后代组成。确定这种共同祖先取决于基因是否具有保守的侧翼序列集，因为从氨基酸序列无法识别这些关系。其中一个基因既产生了一群鱼类β-胸腺素，也产生了鸟类和爬行动物迄今尚未被识别的β-胸腺素群。由此产生的分类法可能有助于与斑马鱼等模式生物的β-胸腺素相关，并有助于识别重要的非编码序列元件，这里举例说明了β4 亚家族转录本 3'非翻译区中的一个保守序列。
