Characterization of unconventional kinetochore kinases KKT10 and KKT19 in Trypanosoma brucei.

Midori Ishii,Bungo Akiyoshi

doi:10.1242/jcs.240978

Abstract

ABSTRACTThe kinetochore is a macromolecular protein complex that drives chromosome segregation in eukaryotes. Unlike most eukaryotes that have canonical kinetochore proteins, evolutionarily divergent kinetoplastids, such as Trypanosoma brucei, have unconventional kinetochore proteins. T. brucei also lacks a canonical spindle checkpoint system, and it therefore remains unknown how mitotic progression is regulated in this organism. Here, we characterized, in the procyclic form of T. brucei, two paralogous kinetochore proteins with a CLK-like kinase domain, KKT10 and KKT19, which localize at kinetochores in metaphase but disappear at the onset of anaphase. We found that these proteins are functionally redundant. Double knockdown of KKT10 and KKT19 led to a significant delay in the metaphase to anaphase transition. We also found that phosphorylation of two kinetochore proteins, KKT4 and KKT7, depended on KKT10 and KKT19 in vivo. Finally, we showed that the N-terminal part of KKT7 directly interacts with KKT10 and that kinetochore localization of KKT10 depends not only on KKT7 but also on the KKT8 complex. Our results reveal that kinetochore localization of KKT10 and KKT19 is tightly controlled to regulate the metaphase to anaphase transition in T. brucei.This article has an associated First Person interview with the first author of the paper.

Highlights

Proper segregation of chromosomes into two daughter cells during cell division is essential for the survival of all eukaryotes
KKT10/19 have an identical protein kinase domain (Fig. 1A), it remained unclear whether they have distinct functions
We obtained a similar result for KKT19 depletion, suggesting that KKT10 and KKT19 may be functionally redundant in procyclic cells

Summary

Introduction

Proper segregation of chromosomes into two daughter cells during cell division is essential for the survival of all eukaryotes. Chromosomes are replicated during S phase and linked together by cohesin complexes (Nasmyth and Haering, 2009). Kinetochore– microtubule attachments are monitored by a feedback mechanism called the spindle checkpoint, which delays the metaphase to anaphase transition until all chromosomes are attached to spindle microtubules emanating from opposite poles (Hoyt et al, 1991; Li and Murray, 1991). Spindle checkpoint components, such as Mad, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK

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