Centromere-associated repeat arrays on Trypanosoma brucei chromosomes are much more extensive than predicted
1 Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
2 Laboratorio de Parasitologia - Facultad de Medicina, Universidad Nacional de Colombia-Sede, Bogota, Columbia
3 Laboratory of Cellular and Structural Biology, Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
BMC Genomics 2012, 13:29 doi:10.1186/1471-2164-13-29Published: 18 January 2012
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.