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XB-ART-49829
Biophys J 2014 Feb 18;1064:875-82. doi: 10.1016/j.bpj.2014.01.005.
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CENP-A arrays are more condensed than canonical arrays at low ionic strength.

Geiss CP, Keramisanou D, Sekulic N, Scheffer MP, Black BE, Frangakis AS.


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The centromeric histone H3 variant centromeric protein A (CENP-A), whose sequence is the least conserved among all histone variants, is responsible for specifying the location of the centromere. Here, we present a comprehensive study of CENP-A nucleosome arrays by cryo-electron tomography. We see that CENP-A arrays have different biophysical properties than canonical ones under low ionic conditions, as they are more condensed with a 20% smaller average nearest-neighbor distance and a 30% higher nucleosome density. We find that CENP-A nucleosomes have a predominantly crossed DNA entry/exit site that is narrowed on average by 8°, and they have a propensity to stack face to face. We therefore propose that CENP-A induces geometric constraints at the nucleosome DNA entry/exit site to bring neighboring nucleosomes into close proximity. This specific property of CENP-A may be responsible for generating a fundamental process that contributes to increased chromatin fiber compaction that is propagated under physiological conditions to form centromeric chromatin.

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Species referenced: Xenopus laevis
Genes referenced: cenpa

References [+] :
Allshire, Epigenetic regulation of centromeric chromatin: old dogs, new tricks? 2008, Pubmed