Université de Strasbourg

CENP-A centromeric histone

Mechanisms of CENP-A assembly and Propagation at Centromeres

Fellow USIAS : Ali Hamiche

The centromere is a specialized region localized at the site of primary constriction of the chromosome in eukaryotic cells. The centromere is of vital importance for genetic stability, and defects in centromere structure result in chromosome mis-segregation, aneuploidy and cancer. Because the DNA sequence of centromeres is not conserved, it is widely accepted that a protein, termed CENP-A (centromere protein-A) is the epigenetic marker of the centromeres. CENP-A is a specialized histone variant which replaces conventional histone H3 at the centromere. Incorporation of CENP-A confers novel structural and functional properties to the nucleosome for which the molecular basis is not known.

In this proposal, we will focus on the structure and function of CENPA in kinetochore assembly and centromere activity, and we will study in detail the role of this histone variant in developing human diseases such as cancer. We propose to study how CENP-A, the key epigenetic player in centromere organization and identity, is deposited to the centromere and which are the factors involved in this process. We will identify such new factors and analyze how they function in a series of in vivo and in vitro experiments. Our preliminary data suggests that a novel kinase is implicated in CENP-A deposition and novel experiments aiming at understanding its function are in progress. Ablation of this kinase leads to CENP-A mislocalization and chromosome mis-segregation. We will use super-resolution light microscopy (ground-state depletion, GSD, related with STORM) to study the mechanism of CENP-A deposition by its chaperone HJURP. We will combine super-resolution light microscopy and advanced high-resolution single particle cryo electron microscopy (cryo-EM) to study the 3D architecture of CENP-A chromatin and associated complexes. The expected data will reveal how a plethora of crucial epigenetic factors function in maintaining genomic stability. Shedding light on the CENP-A functions is of crucial importance for understanding the mechanism of active kinetochore assembly and thus, the epigenetic origins of chromosome instability in diseases.


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