By:
Fredrik Hurtig, MBW, Stockholm University
Supervisor:
Ann-Christin Lindås, MBW, Stockholm University
Opponent:
Lionel Guy, Department of Medical Biochemistry andf Microbiology, Uppsala University
Committée:
Edouard Pesquet, DEEP, Stockholm University
Arne Lindqvist, Department of Cell- and Molecular Biology, Karolinska intitutet
Linda Sandblad, Department of Chemistry, Umeå University
Chairman:
Anders Nilsson, MBW, Stockholm University

Digitally via Zoom: Zoom Meeting ID: 638-3943-9290,
https://stockholmuniversity.zoom.us/j/63839439290

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Divisive structures

Two billions years of biofilament evolution

Abstract
Our understanding of the functional and regulatory complexity that existed in the eukaryotic progenitor is poor, and
investigations have been hindered by our nebulous understanding of where eukaryotes stem from. Recently  discovered archaeal lineages with hitherto unseen homology to eukaryotic systems suggest archaea can further our understanding of the eukaryotic cell’s ancestry. However, much of archaeal biology remains largely unexplored. Two eukaryotic systems with archaeal homologues, namely the actin and ESCRT-III protein filament systems, are essential for diverse processes in eukaryotic biology. In this thesis, we show that an archaeal homologue of ESCRT-III divides the cell under proteasomal regulation, a regulatory mechanism central to eukaryotic cell cycle regulation. Additionally, we show how predicted putative profilin and gelsolin homologues regulate the postulated proto-cytoskeleton of Asgard archaea. In investigating the function and regulation of these archaeal systems we demonstrate compelling parallels between archaeal and eukaryotic regulatory strategies which stresses the close evolutionary relationship that exists between these two domains.

Keywords: Evolution, Archaea, Eukaryogenesis, ESCRT-III, Actin, Profilin, Gelsolin, Asgard, TACK, Sulfolobus, Cell division, Cytokinesis, Cytoskeleton, Heimdallarchaeota, Actin-binding protein.