# A role for β-1,6- and β-1,3-glucans in kinetochore function in Saccharomyces cerevisiae

## TL;DR

This study reveals that enzymes involved in yeast cell wall synthesis also play a role in kinetochore function, which is essential for proper chromosome segregation during cell division.

## Contribution

The paper discovers a novel regulatory role for β-1,6- and β-1,3-glucan biosynthesis enzymes in kinetochore function in yeast.

## Key findings

- Deletion of KRE6 suppresses centromeric defects in kinetochore components like NDC80 and MIND.
- Reduction of intracellular β-glucans, not cell wall content, regulates kinetochore function.
- Kre6 physically interacts with CENP-A/Cse4, suggesting a direct role in kinetochore regulation.

## Abstract

Chromosome segregation is crucial for the faithful inheritance of DNA to the daughter cells after DNA replication. For this, the kinetochore, a megadalton protein complex, assembles on centromeric chromatin containing the histone H3 variant CENP-A, and provides a physical connection to the microtubules. Here, we report an unanticipated role for enzymes required for β-1,6- and β-1,3-glucan biosynthesis in regulating kinetochore function in Saccharomyces cerevisiae. These carbohydrates are the major constituents of the yeast cell wall. We found that the deletion of KRE6, which encodes a glycosylhydrolase/ transglycosidase required for β-1,6-glucan synthesis, suppressed the centromeric defect of mutations in components of the kinetochore, foremost the NDC80 components Spc24, Spc25, the MIND component Nsl1, and Okp1, a constitutive centromere-associated network protein. Similarly, the absence of Fks1, a β-1,3-glucan synthase, and Kre11/Trs65, a TRAPPII component, suppressed a mutation in SPC25. Genetic analysis indicates that the reduction of intracellular β-1,6- and β-1,3-glucans, rather than the cell wall glucan content, regulates kinetochore function. Furthermore, we found a physical interaction between Kre6 and CENP-A/Cse4 in yeast, suggesting a potential function for Kre6 in glycosylating CENP-A/Cse4 or another kinetochore protein. This work shows a moonlighting function for selected cell wall synthesis proteins in regulating kinetochore assembly, which may provide a mechanism to connect the nutritional status of the cell to cell-cycle progression and chromosome segregation.