Shearing of the CENP-A dimerization interface mediates plasticity in the octameric centromeric nucleosome

D Winogradoff, H Zhao, Y Dalal, GA Papoian - Scientific reports, 2015 - nature.com
Scientific reports, 2015nature.com
The centromeric nucleosome is a key epigenetic determinant of centromere identity and
function. Consequently, deciphering how CENP-A containing nucleosomes contribute
structurally to centromere function is a fundamental question in chromosome biology. Here,
we performed microsecond timescale all-atom molecular dynamics (MD) simulations of
CENP-A and H3 nucleosomes and report that the octameric CENP-A core particles and
nucleosomes display different dynamics from their canonical H3-containing counterparts …
Abstract
The centromeric nucleosome is a key epigenetic determinant of centromere identity and function. Consequently, deciphering how CENP-A containing nucleosomes contribute structurally to centromere function is a fundamental question in chromosome biology. Here, we performed microsecond timescale all-atom molecular dynamics (MD) simulations of CENP-A and H3 nucleosomes and report that the octameric CENP-A core particles and nucleosomes display different dynamics from their canonical H3-containing counterparts. The most significant motion observed is within key interactions at the heart of the CENP-A octameric core, wherein shearing of contacts within the CENP-A:CENP-A’ dimerization interface results in a weaker four helix bundle and an extrusion of 10–30 bp of DNA near the pseudo-dyad. Coupled to other local and global fluctuations, the CENP-A nucleosome occupies a more rugged free energy landscape than the canonical H3 nucleosome. Taken together, our data suggest that CENP-A encodes enhanced distortability to the octameric nucleosome, which may allow for enhanced flexing of the histone core in vivo.
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