Histone variants in archaea and the evolution of combinatorial chromatin complexity
Kathryn M Stevens, Jacob B. Swadling, Antoine Hocher, Corinna Bang, Simonetta Gribaldo, Ruth A. Schmitz, Tobias Warnecke
Abstract
that are characterized by unstable interfaces between dimers. We propose that these paralogs act as capstones that prevent stable tetramer formation and extension into longer oligomers characteristic of model archaeal histones. Importantly, we provide evidence from phylogeny and genome architecture that these capstones, as well as other paralogs in the Methanobacteriales, have been maintained for hundreds of millions of years following ancient duplication events. Taken together, our findings indicate that at least some archaeal histone paralogs have evolved to play distinct and conserved functional roles, reminiscent of eukaryotic histone variants. We conclude that combinatorially complex histone-based chromatin is not restricted to eukaryotes and likely predates their emergence.