Styles Pamela, Brookfield John F Y
Institute of Genetics, School of Biology, University of Nottingham, Nottingham, UK.
BMC Evol Biol. 2009 May 14;9:102. doi: 10.1186/1471-2148-9-102.
Alu elements are a family of SINE retrotransposons in primates. They are classified into subfamilies according to specific diagnostic mutations from the general Alu consensus. It is now believed that there may be several retrotranspositionally-competent source genes within an Alu subfamily. In this study, subfamilies falling on the AluYi and AluYh lineages, and the AluYg6 subfamily, are assessed for the presence of secondary source genes, and the influence of gene conversion on the AluYh and AluYi lineages is also described.
The AluYh7 and AluYi6 subfamilies appear to contain multiple source genes. The novel subfamilies AluYh3a1 and AluYh3a3 are described, for which there is no convincing evidence to suggest the presence of secondary sources. The mutational substructure of AluYh3a3 can be explained completely by inference of single master gene. A complete backwards gene conversion event appears to have inactivated the AluYh3a3 master gene in humans. Polymorphism data suggest a larger number of secondary source elements may be active in the AluYg6 family than previously thought.
It is clear that there is considerable variation in the number of source genes present in each of the young Alu subfamilies. This can range from a single master source gene, as for AluYh3a3, to as many as 14 source elements in AluYi6.
Alu元件是灵长类动物中的一类短散在核元件（SINE）反转录转座子。它们根据与通用Alu共有序列的特定诊断性突变被分类为亚家族。现在人们认为，一个Alu亚家族中可能存在多个具有反转录转座活性的源基因。在本研究中，对属于AluYi和AluYh谱系的亚家族以及AluYg6亚家族进行了评估，以确定是否存在二级源基因，并描述了基因转换对AluYh和AluYi谱系的影响。
AluYh7和AluYi6亚家族似乎包含多个源基因。描述了新的亚家族AluYh3a1和AluYh3a3，没有令人信服的证据表明它们存在二级源。AluYh3a3的突变亚结构可以通过单个主基因的推断完全解释。一个完整的反向基因转换事件似乎使人类中的AluYh3a3主基因失活。多态性数据表明，AluYg6家族中可能有比以前认为的更多的二级源元件具有活性。
显然，每个年轻的Alu亚家族中存在的源基因数量存在相当大 的差异。这一差异范围从像AluYh3a3那样的单个主源基因，到AluYi6中的多达14个源元件。
