ChTOG is a conserved mitotic error correction factor.

Jacob A Herman,Matthew P Miller,Sue Biggins

doi:10.7554/elife.61773

Abstract

Accurate chromosome segregation requires kinetochores on duplicated chromatids to biorient by attaching to dynamic microtubules from opposite spindle poles, which exerts forces to bring kinetochores under tension. However, kinetochores initially bind to microtubules indiscriminately, resulting in errors that must be corrected. While the Aurora B protein kinase destabilizes low-tension attachments by phosphorylating kinetochores, low-tension attachments are intrinsically less stable than those under higher tension in vitro independent of Aurora activity. Intrinsic tension-sensitive behavior requires the microtubule regulator Stu2 (budding yeast Dis1/XMAP215 ortholog), which we demonstrate here is likely a conserved function for the TOG protein family. The human TOG protein, chTOG, localizes to kinetochores independent of microtubules by interacting with Hec1. We identify a chTOG mutant that regulates microtubule dynamics but accumulates erroneous kinetochore-microtubule attachments that are not destabilized by Aurora B. Thus, TOG proteins confer a unique, intrinsic error correction activity to kinetochores that ensures accurate chromosome segregation.

Highlights

Eukaryotic cell division requires the duplication and accurate segregation of up to hundreds of chromosomes
The microtubule cytoskeleton is organized into a bipolar spindle such that each and every pair of duplicated sister chromosomes becomes bioriented
We used engineered HCT116 cells where the endogenous chTOG genes were epitope tagged with EGFP (Cherry et al, 2019) to determine whether chTOG localizes to kinetochores throughout mitosis (Figure 1a)

Summary

Introduction

Eukaryotic cell division requires the duplication and accurate segregation of up to hundreds of chromosomes. Stu and the entire Dis1/XMAP215 family are well-characterized microtubule regulators that contribute to the nucleation, polymerization, and organization of the cytoskeleton and spindle in both developing and somatic cells (Brouhard et al, 2008; Cullen et al, 1999; Gard and Kirschner, 1987; Kosco et al, 2001; Milunovic-Jevtic et al, 2018; Roostalu et al, 2015; Shirasu-Hiza et al, 2003) This protein family is thought to accomplish these diverse forms of microtubule regulation through two regulatory regions. We recently described a Stu mutant that supported spindle formation in yeast cells, but not biorientation, which provided in vivo evidence that Stu functions as an error correction factor independent of its role organizing the mitotic spindle (Miller et al, 2019). Our work further elucidates a largely uncharacterized, intrinsic mechanism by which kinetochores sense and respond to biomolecular forces in order to prevent errors in chromosome segregation

Results

Discussion

Materials and methods