Abstract

BackgroundThe centromere is the specialized locus required for correct chromosome segregation during cell division. The DNA of most eukaryotic centromeres is composed of extended arrays of tandem repeats (satellite DNA). In the horse, we previously showed that, although the centromere of chromosome 11 is completely devoid of tandem repeat arrays, all other centromeres are characterized by the presence of satellite DNA. We isolated three horse satellite DNA sequences (37cen, 2P1 and EC137) and described their chromosomal localization in four species of the genus Equus.ResultsIn the work presented here, using the ChIP-seq methodology, we showed that, in the horse, the 37cen satellite binds CENP-A, the centromere-specific histone-H3 variant. The 37cen sequence bound by CENP-A is GC-rich with 221 bp units organized in a head-to-tail fashion. The physical interaction of CENP-A with 37cen was confirmed through slot blot experiments. Immuno-FISH on stretched chromosomes and chromatin fibres demonstrated that the extension of satellite DNA stretches is variable and is not related to the organization of CENP-A binding domains. Finally, we proved that the centromeric satellite 37cen is transcriptionally active.ConclusionsOur data offer new insights into the organization of horse centromeres. Although three different satellite DNA families are cytogenetically located at centromeres, only the 37cen family is associated to the centromeric function. Moreover, similarly to other species, CENP-A binding domains are variable in size. The transcriptional competence of the 37cen satellite that we observed adds new evidence to the hypothesis that centromeric transcripts may be required for centromere function.Electronic supplementary materialThe online version of this article (doi:10.1186/s13039-016-0242-z) contains supplementary material, which is available to authorized users.

Highlights

  • The centromere is the specialized locus required for correct chromosome segregation during cell division

  • Molecular identification of the functional centromeric satellite DNA The aim of the present work was to define the satellite DNA repeats bearing the centromeric function in the horse

  • The CREST signals always colocalized with the 37cen fluorescence, no clear correlation seemed to exist between intensity and extension of the 37cen and the CREST signals. These results suggest that, at horse centromeres, the size of centromere protein A (CENP-A) binding domains is not related to the extent of satellite DNA stretches; these finding are in agreement with the well described inter- and intraspecific variability of the molecular organization of eukaryotic centromeres [6]

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Summary

Introduction

The centromere is the specialized locus required for correct chromosome segregation during cell division. We previously showed that, the centromere of chromosome 11 is completely devoid of tandem repeat arrays, all other centromeres are characterized by the presence of satellite DNA. Following our initial description of a centromere completely devoid of satellite DNA in the horse [9], other examples of naturally occurring satellite-less centromeres were observed in plants and animals [10,11,12,13]. These observations raise the challenging question whether centromeric and pericentromeric satellites have a functional role. Satellite DNA may facilitate binding of the centromere specific histone CENP-A (the main epigenetic mark of centromere function) to centromeric chromatin

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