Arcot S S, Wang Z, Weber J L, Deininger P L, Batzer M A
Human Genome Center, Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
Genomics. 1995 Sep 1;29(1):136-44. doi: 10.1006/geno.1995.1224.
As a result of their abundance, relatively uniform distribution, and high degree of polymorphism, microsatellites and minisatellites have become valuable tools in genetic mapping, forensic identity testing, and population studies. In recent years, a number of microsatellite repeats have been found to be associated with Alu interspersed repeated DNA elements. The association of an Alu element with a microsatellite repeat could result from the integration of an Alu element within a preexisting microsatellite repeat. Alternatively, Alu elements could have a direct role in the origin of microsatellite repeats. Errors introduced during reverse transcription of the primary transcript derived from an Alu "master" gene or the accumulation of random mutations in the middle A-rich regions and oligo(dA)-rich tails of Alu elements after insertion and subsequent expansion and contraction of these sequences could result in the genesis of a microsatellite repeat. We have tested these hypotheses by a direct evolutionary comparison of the sequences of some recent Alu elements that are found only in humans and are absent from nonhuman primates, as well as some older Alu elements that are present at orthologous positions in a number of nonhuman primates. The origin of "young" Alu insertions, absence of sequences that resemble microsatellite repeats at the orthologous loci in chimpanzees, and the gradual expansion of microsatellite repeats in some old Alu repeats at orthologous positions within the genomes of a number of nonhuman primates suggest that Alu elements are a source for the genesis of primate microsatellite repeats.
由于微卫星和小卫星数量丰富、分布相对均匀且多态性程度高，它们已成为基因图谱绘制、法医身份鉴定和群体研究中的重要工具。近年来，人们发现一些微卫星重复序列与Alu散布重复DNA元件有关。Alu元件与微卫星重复序列的关联可能是由于Alu元件整合到了预先存在的微卫星重复序列中。或者，Alu元件可能在微卫星重复序列的起源中起直接作用。Alu“主”基因初级转录本逆转录过程中引入的错误，或者Alu元件插入后中间富含A区域和富含寡聚(dA)尾巴中随机突变的积累，以及这些序列随后的扩增和收缩，可能导致微卫星重复序列的产生。我们通过对一些仅在人类中发现而在非人类灵长类动物中不存在的近期Alu元件序列，以及一些在许多非人类灵长类动物直系同源位置存在的较古老Alu元件序列进行直接进化比较，来检验这些假设。“年轻”Alu插入序列的起源、黑猩猩直系同源位点上不存在类似微卫星重复序列的情况，以及一些非人类灵长类动物基因组中直系同源位置的一些古老Alu重复序列中微卫星重复序列的逐渐扩增，表明Alu元件是灵长类微卫星重复序列产生的一个来源。
