Abstract
BackgroundAfrican 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.ResultsWe 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.ConclusionsOur 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.
Highlights
African trypanosomes belong to a eukaryotic lineage which displays many unusual genetic features
Using the etoposide mapping method, we identified the location of putative centromeric domains on the 8 T. brucei chromosomes that had been fully assembled [18]
The locations of centromeric regions on T. brucei chromosomes 9 - 11 have been predicted from etoposidemediated mapping [19], incomplete assembly of the corresponding regions negates accurate longrange restriction mapping
Summary
African trypanosomes belong to a eukaryotic lineage which displays many unusual genetic features. Centromeres in Trypanosoma brucei have been localised to chromosomal regions that contain an array of ~147 bp AT-rich tandem repeats. Centromeres are the chromosomal loci that facilitate segregation in most eukaryotes. They are the site of assembly of the kinetochore, the nucleoprotein complex which anchors the microtubule spindles that separate sister chromatids and mediate their movement to the daughter nuclei. The repeats are generally restricted to centromeric regions and are often in the size range 150 - 180 bp. This length is similar to that of nucleosomes, a property that may be of functional significance [6].
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