Structural Basis for Centromere-Mediated Control of Error-free Chromosome Segregation

Accurate chromosome segregation during cell division requires bipolar attachment of sister-chromatids to microtubules emanating from opposite spindle poles and maintenance of sister-chromatid cohesion until all chromosomes achieve bi-orientation. Two chromosomal sites regulate these processes: centromeres, the microtubule attachment sites defined by the enrichment of CENP-A nucleosomes, and the inner centromere, a region between the sister-chromatids that recruits enzymatic activities (kinases, phosphatases and motor proteins). The inner centromere associated enzymes selectively stabilise chromosome-microtubule attachments suitable for chromosome bi-orientation, control sister chromatid cohesion and achieve timely chromosome segregation. Errors in these processes can lead to aneuploidy, a numerical chromosomal aberration implicated in miscarriages, birth defects and cancers. Using an integrative structure-function approach (X-ray crystallography, cryo electron microscopy, Crosslinking/Mass Spectrometry, biochemical/biophysical methods with human cell-line based functional assays), we will obtain detailed mechanistic understanding of: (1) how the inner centromere is assembled, (2) how the inner centromere associated interaction network recruits regulators to achieve chromosome bi-orientation and accurate segregation, and (3) how centromere identity is maintained through multiple generations. This work builds on our recently obtained exciting structural/molecular knowledge that have led to unexpected insights and new questions and will exploit our recently generated battery of molecular reagents. Outcome of our work will provide unprecedented details of centromere-mediated control of chromosome segregation and allow us to build a comprehensive mechanistic model for error-free chromosome segregation, a process that has been fascinating researchers for more than a century.