Thomas Sean, Westenberger Scott J, Campbell David A, Sturm Nancy R
Molecular Biology Institute, University of California, Los Angeles, CA, USA.
Gene. 2005 Jun 6;352:100-8. doi: 10.1016/j.gene.2005.04.002.
The spliced leader RNA gene (SL RNA) repeat is present in large multicopy arrays and has been used as a marker for the diversity of kinetoplastid protozoans. Intra-array variation could affect conclusions made using a randomly isolated repeat as a marker. We examined the Leishmania major (Friedlin) and Trypanosoma cruzi (CL Brener) genome projects for SL RNA repeat sequences in order to assess their homogeneity and the possible effects of sequence variation on taxonomic interpretation. Of the dozens of distinct sequence classes examined, no single copy would bias clustering analyses with regard to other closely related species or isolates. Six dimorphic sites within the T. cruzi transcribed region were found to be linked and are predicted to yield a heterogeneous SL RNA population. The variation that exists among the repeats paints a picture of the broad mechanisms of array maintenance and evolution where site-specific mutations in a single repeat may be spread throughout the array and recombined with existing repeats to create new sequence classes, all occurring under selective pressure to maintain or increase the fitness of the cell line in which these events occur.
剪接前导RNA基因（SL RNA）重复序列存在于大型多拷贝阵列中，并已被用作动质体原生动物多样性的标记。阵列内的变异可能会影响使用随机分离的重复序列作为标记得出的结论。我们研究了利什曼原虫（Friedlin）和克氏锥虫（CL Brener）基因组计划中的SL RNA重复序列，以评估它们的同质性以及序列变异对分类学解释的可能影响。在所检查的数十种不同序列类别中，没有单个拷贝会在与其他密切相关的物种或分离株的聚类分析中产生偏差。在克氏锥虫转录区域内发现六个双态位点是连锁的，预计会产生异质的SL RNA群体。重复序列之间存在的变异描绘了阵列维持和进化的广泛机制，其中单个重复序列中的位点特异性突变可能会扩散到整个阵列，并与现有重复序列重组以产生新的序列类别，所有这些都在选择压力下发生，以维持或提高发生这些事件的细胞系的适应性。
