Fig. 3.

TEs and the evolution of centromeres. An initial destabilization event leads to the formation of a neocentromere (black dot indicates new centromere location, open circle indicates former centromere location on an ideogram representation of a chromosome), linked to the transcription of a TE (purple) in the absence of satellite DNA (gray). Following recruitment of CENP-A nucleosomes (yellow), more TEs insertions occur and incorporation of CENP-A nucleosomes (yellow, other H3-containing nucleosomes are indicated by blue) spread to form a complex centromere. As the complex centromere establishes an equilibrium state, TEs accumulate and satellites (arrowheads) begin to emerge. While individual variation in the placement of CENP-A nucleosomes (CENP-A containing nucleosomes are yellow, other centromeric H3-nucleosomes are blue, non-centromeric nucleosomes are brown) can exist within a population, the average centromere domain is relatively stable. At this stage of centromere evolution, interchromosomal movement of TEs can influence homogenization of arrays across non-homologous chromosomes. Finally, a dominant satellite emerges that subsequently forms higher order arrays with only intermittent TE insertions. Following a chromosome destabilization event, the HOR is either inactivated by unknown mechanisms, or lost due to chromosome damage, and a new centromere emerges in a different location