Journal
MOLECULAR BIOLOGY OF THE CELL
Volume 33, Issue 14, Pages -Publisher
AMER SOC CELL BIOLOGY
DOI: 10.1091/mbc.E22-07-0269-T
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Funding
- Wellcome Trust [210622/Z/18/Z]
- Wellcome Trust [210622/Z/18/Z] Funding Source: Wellcome Trust
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The kinetoplastid parasite Trypanosoma brucei has unique kinetochore proteins, KKT2 and KKT3, which play important roles in chromosome segregation. KKT2's kinase activity is essential for accurate chromosome segregation, while KKT3's kinase activity is dispensable for cell growth. The divergent polo boxes of KKT2 and KKT3 initiate kinetochore assembly and interact with other kinetochore proteins.
Chromosome segregation requires assembly of the macromolecular kinetochore complex onto centromeric DNA. While most eukaryotes have canonical kinetochore proteins that are widely conserved among eukaryotes, evolutionarily divergent kinetoplastids have a unique set of kinetochore proteins. Little is known about the mechanism of kinetochore assembly in kinetoplastids. Here we characterize two homologous kinetoplastid kinetochore proteins, KKT2 and KKT3, that constitutively localize at centromeres. They have three domains that are highly conserved among kinetoplastids: an N-terminal kinase domain of unknown function, the centromere localization domain in the middle, and the C-terminal domain that has weak similarity to polo boxes of Polo-like kinases. We show that the kinase activity of KKT2 is essential for accurate chromosome segregation, while that of KKT3 is dispensable for cell growth in Trypanosoma brucei. Crystal structures of their divergent polo boxes reveal differences between KKT2 and KKT3. We also show that the divergent polo boxes of KKT3 are sufficient to recruit KKT2 in trypanosomes. Furthermore, we demonstrate that the divergent polo boxes of KKT2 interact directly with KKT1 and that KKT1 interacts with KKT6. These results show that the divergent polo boxes of KKT2 and KKT3 are protein-protein interaction domains that initiate kinetochore assembly in T. brucei.
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