Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
BMC Genomics. 2012 Jan 18;13:29. doi: 10.1186/1471-2164-13-29.
African trypanosomes belong to a eukaryotic lineage which displays many unusual genetic features. The mechanisms of chromosome segregation in these diploid protozoan parasites are poorly understood. Centromeres in Trypanosoma brucei have been localised to chromosomal regions that contain an array of ~147 bp AT-rich tandem repeats. Initial estimates from the genome sequencing project suggested that these arrays ranged from 2 - 8 kb. In this paper, we show that the centromeric repeat regions are much more extensive.
We used a long-range restriction endonuclease mapping approach to more accurately define the sizes of the centromeric repeat arrays on the 8 T. brucei chromosomes where unambiguous assembly data were available. The results indicate that the sizes of the arrays on different chromosomes vary from 20 to 120 kb. In addition, we found instances of length heterogeneity between chromosome homologues. For example, values of 20 and 65 kb were obtained for the arrays on chromosome 1, and 50 and 75 kb for chromosome 5.
Our results show that centromeric repeat arrays on T. brucei chromosomes are more similar in size to those of higher eukaryotes than previously suspected. This information provides a firmer framework for investigating aspects of chromosome segregation and will allow epigenetic features associated with the process to be more accurately mapped.
非洲锥体虫属于真核生物谱系，具有许多不寻常的遗传特征。这些二倍体原生动物寄生虫的染色体分离机制尚未得到充分理解。在布氏锥虫中，着丝粒已被定位到含有一系列约 147bp 的 AT 富含串联重复序列的染色体区域。基因组测序项目的初步估计表明，这些阵列的范围从 2-8kb。在本文中，我们表明着丝粒重复区域要广泛得多。
我们使用长距离限制内切酶作图方法，更准确地定义了在 8 个 T. brucei 染色体上着丝粒重复阵列的大小，这些染色体具有明确的组装数据。结果表明，不同染色体上阵列的大小从 20kb 到 120kb 不等。此外，我们还发现染色体同源物之间存在长度异质性的实例。例如，在染色体 1 上获得了 20kb 和 65kb 的值，在染色体 5 上获得了 50kb 和 75kb 的值。
我们的结果表明，T. brucei 染色体上着丝粒重复阵列的大小与先前怀疑的高等真核生物更为相似。该信息为研究染色体分离的各个方面提供了更坚实的框架，并将允许更准确地绘制与该过程相关的表观遗传特征。
