FBS Colloquia No.394Laboratory of Chromosome Biology

Maintaining genome integrity: Proximity labeling uncovers hidden controls in chromosome segregation

Accurate chromosome segregation during cell division is essential for organismal growth, health and development, as errors can lead to aneuploidy and disease, notably cancer. At the heart of this process is the kinetochore, a multiprotein structure that connects chromosomes to spindle microtubules. Yet, we do not fully understand how the multi-complex kinetochore structure is assembled and stably maintained during each division. In this talk, I will share our recent discovery of two spatially distinct regulatory mechanisms that collectively control the stability of a key pillar of the kinetochore, the CENP-T complex. CENP-T, together with CENP-W, -S, and -X, forms a nucleosome-like complex that links centromeric chromatin to the outer kinetochore, ensuring proper microtubule attachment and genome stability. Unexpectedly, we find that the CENP-T complex undergoes rapid turnover during the cell cycle. To identify regulators of CENP-T complex stability and turnover, we used an unbiased, sensitive proximity-labeling-based proteomic screen, uncovering a network of factors acting at both the complex and sub-unit levels. Our follow-up investigations revealed two mechanisms that collectively enable CENP-T stability and functionality. These mechanisms are redundant yet synergistic, reflecting their essential role in preserving genome stability. Importantly, this two-layered control is conserved across vertebrate species and highlights a potential vulnerability in rapidly dividing disease cells. Together, our work reshapes our understanding of kinetochore homeostasis and offers new perspectives for targeting genome stability mechanisms in disease.