Ancient co-option of LTR retrotransposons as yeast centromeres

ABSTRACT: Centromeres ensure accurate chromosome segregation, yet their DNA evolves rapidly across eukaryotes, leaving the origin of new centromere architectures unresolved. In the brewer’s yeast Saccharomyces cerevisiae (order Saccharomycetales), compact, genetically defined “point” centromeres replaced large, repeat-rich, epigenetically specified centromeres, but how this transition occurred has been unclear. Competing models have proposed either descent with modification from ancestral epigenetic centromeres or acquisition from selfish plasmid DNA. Here we map and characterize centromeres in the sister order Saccharomycodales and identify evolutionarily related “proto-point” centromeres that bridge repeat-rich and point centromeres. Proto-point centromeres contain a single centromeric nucleosome positioned over an AT-rich core, but retain relaxed organization and sequence variability in flanking cis-elements. In two species, including Saccharomycodes ludwigii, proto-point centromeres are embedded within clusters of Ty5 long terminal repeat (LTR) retrotransposons, and their core CDEII and flanking motifs share sequence similarity to Ty5 LTR sequence. Comparative genomics, synteny, and phylogenetic analyses across multiple yeast orders show that Ty5-cluster centromeres are ancient genomic features and support a model in which proto-point and point centromeres evolved by co-option of Ty5 LTR sequences in an ancestor with retrotransposon-rich centromeres, rather than by horizontal transfer from the 2-µm plasmid. These results indicate that yeast point centromeres are direct descendants of retrotransposons and illustrate how transposable elements can be repurposed to create genetically encoded centromeres.

ORGANISM(S): Hanseniaspora uvarum

PROVIDER: GSE294411 | GEO | 2025/12/15

REPOSITORIES: GEO