Séminaire IJM – Nick Irwin

Invité par l’équipe Duharcourt, Nick Irwin (Gregor Mendel Institute, Vienna BioCenter) présentera un séminaire de l’Institut Jacques Monod sur le thème :

Self-assembling viral histones unravel early nucleosome evolution

Résumé :

The nucleosome is a defining feature of eukarytoes that plays a central role in the coordination and regulation of the genome. Accordingly, understanding the origin of the nucleosome is essential for interpreting how eukaryotes evolved from prokaryotic ancestors. The strong conservation of the nucleosome and its histone constituents makes reconstructing nucleosome evolution challenging, but divergent histone homologues found in large double stranded DNA viruses could provide a new perspective for interpreting the evolution of this complex. By surveying viral diversity, we identified hundreds of viral histones with unique protein architectures, including histone quadruplets which comprise the four core histones linked in series. These viral histones branch phylogenetically between Archaea and eukaryotes and display intermediate structural and functional characteristics, self-assembling into eukaryotic-like nucleosomes that stack into archaeal-like oligomers. Finally, we demonstrate how histone linkage can facilitate nucleosome assembly, permitting the formation of animal nucleosomes in the bacterium Escherichia coli. I will discuss how these data can help us understand not only the origin of viral histones, but lead to an empirically based hypothesis for the origin of the nucleosome.