Evidence of 14-3-3 proteins contributing to kinetochore integrity and chromosome congression during mitosis.

The 14-3-3 family of proteins are conserved across eukaryotes and serve myriad important regulatory functions of the cell. Homo/heterodimers of these protein homologs, majorly recognize their ligands via conserved motifs to modulate the localization and functions of those effector ligands. In most of the genetic backgrounds of Saccharomyces cerevisiae, disruption of both 14-3-3 homologs (Bmh1 and Bmh2) are either lethal or survive with severe growth defects showing gross chromosomal missegregation and prolonged cell cycle arrest. To elucidate their contributions to chromosome segregation, in this work we investigated their centromere/kinetochore-related functions. Analysis of appropriate deletion mutants shows that Bmh isoforms have cumulative and unshared isoform-specific contributions in maintaining the proper integrity of the kinetochore ensemble. Consequently, bmh mutant cells exhibited perturbations in kinetochore-microtubule (KT-MT) dynamics, characterized by kinetochore declustering, mis-localization of kinetochore proteins, and Mad2-mediated transient G2/M arrest. These defects also caused an asynchronous chromosome congression in bmh mutants during metaphase. In summary, this report advances the knowledge on contributions of budding yeast 14-3-3 proteins in chromosome segregation by demonstrating their roles in kinetochore integrity and chromosome congression.