Lehoczky Jessica A, Innis Jeffrey W
Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA.
Evol Dev. 2008 Jul-Aug;10(4):433-8. doi: 10.1111/j.1525-142X.2008.00254.x.
The N-terminal region of human HOXA13 has seven discrete polyalanine tracts. Our previous analysis of these tracts in multiple major vertebrate clades suggested that three are mammal-specific. We now report the N-terminal HOXA13 repetitive tract structures in the monotreme Tachyglossus aculeatus (echidna). Contrary to our expectations, echidna HOXA13 possesses a unique set of polyalanine tracts and an unprecedented polyglycine tract. The data support the conclusion that the emergence of expanded polyalanine tracts in proteins occurred very early in the stem lineage that gave rise to mammals, between 162 and 315 Ma.
人类HOXA13的N端区域有七个离散的聚丙氨酸序列。我们之前对多个主要脊椎动物类群中这些序列的分析表明，其中三个是哺乳动物特有的。我们现在报告单孔目动物针鼹（Tachyglossus aculeatus）中HOXA13 N端重复序列结构。与我们的预期相反，针鼹的HOXA13拥有一组独特的聚丙氨酸序列和一个前所未有的聚甘氨酸序列。这些数据支持这样的结论：蛋白质中扩展的聚丙氨酸序列的出现发生在产生哺乳动物的干群谱系中非常早期的时候，在1.62亿至3.15亿年前。
