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Understanding the mechanism of chromosome segregation: lessons from diversity

Thursday 7 March 2019, 1.00PM

Speaker(s): Dr Bungo Akiyoshi, University of Oxford

Biologists can learn a lot of lessons from exceptions. Although it was widely assumed that the macromolecular protein complex that drives chromosome segregation (called the kinetochore) consists of proteins that are common to all eukaryotes, no canonical kinetochore components have been identified in a group of organisms called kinetoplastids. To reveal how kinetoplastids drive chromosome segregation, we identified 20 kinetochore proteins in Trypanosoma brucei (an experimentally-tractable kinetoplastid parasite that causes human African trypanosomiasis) and discovered that they constitute kinetochores specific to kinetoplastids. We are currently characterizing these unconventional kinetochore proteins in vitro and in vivo to understand how they carry out conserved kinetochore functions. By understanding how kinetoplastids segregate their chromosomes, we aim to understand fundamental principles of chromosome segregation machinery.

Why do kinetoplastids have unique kinetochores, while all the rest of so-far sequenced eukaryotes have conventional ones? This might reflect the evolutionary history of eukaryotes. Although determining the position of the root of the eukaryotic tree of life remains an unresolved problem, one hypothesis places the root between kinetoplastids and all the rest of eukaryotes, meaning that kinetoplastids might be the earliest-branching eukaryotes. It is therefore possible that kinetoplastids evolved the unique kinetochore system early in the eukaryotic history, whereas other eukaryotes evolved a system utilizing conventional kinetochore proteins.

Location: K018