A Satellite-Free Centromere in Chromosome 10.

In mammals, centromeres are epigenetically specified by the histone H3 variant CENP-A and are typically associated with satellite DNA. We previously described the first example of a natural satellite-free centromere on chromosome 11 (ECA11) and, subsequently, on several chromosomes in other species of the genus . We discovered that these satellite-free neocentromeres arose recently during evolution through centromere repositioning and/or chromosomal fusion, after inactivation of the ancestral centromere, where, in many cases, blocks of satellite sequences were maintained.

Robertsonian Fusion and Centromere Repositioning Contributed to the Formation of Satellite-free Centromeres During the Evolution of Zebras.

Centromeres are epigenetically specified by the histone H3 variant CENP-A and typically associated with highly repetitive satellite DNA. We previously discovered natural satellite-free neocentromeres in Equus caballus and Equus asinus. Here, through ChIP-seq with an anti-CENP-A antibody, we found an extraordinarily high number of centromeres lacking satellite DNA in the zebras Equus burchelli (15 of 22) and Equus grevyi (13 of 23), demonstrating that the absence of satellite DNA at the majority of centromeres is compatible with genome stability and species survival and challenging the role of satellite DNA in centromere function.

Telomeric-Like Repeats Flanked by Sequences Retrotranscribed from the Telomerase RNA Inserted at DNA Double-Strand Break Sites during Vertebrate Genome Evolution.

Interstitial telomeric sequences (ITSs) are stretches of telomeric-like repeats located at internal chromosomal sites. We previously demonstrated that ITSs have been inserted during the repair of DNA double-strand breaks in the course of evolution and that some rodent ITSs, called TERC-ITSs, are flanked by fragments retrotranscribed from the telomerase RNA component (TERC). In this work, we carried out an extensive search of TERC-ITSs in 30 vertebrate genomes and identified 41 such loci in 22 species, including in humans and other primates.