Modulated contact frequencies at gene-rich loci support a statistical helix model for mammalian chromatin organization.

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Court, Franck | Miro, Julie | Braem, Caroline | Lelay-Taha, Marie-Noëlle | Brisebarre, Audrey | Atger, Florian | Gostan, Thierry | Weber, Michaël | Cathala, Guy | Forné, Thierry

Edité par CCSD ; BioMed Central -

International audience. ABSTRACT: BACKGROUND: Despite its critical role for mammalian gene regulation, the basic structural landscape of chromatin in living cells remains largely unknown within chromosomal territories below the megabase scale. RESULTS: Here, using the 3C-qPCR method, we investigate contact frequencies at high resolution within the interphase chromatin at several mouse loci. We find that, at several gene-rich loci, contact frequencies undergo a periodical modulation (every 90-100 kb) that affects chromatin dynamics over large genomic distances (few hundred kb). Interestingly, this modulation appears to be conserved in human cells and bioinformatic analyses of locus-specific, long-range cis-interactions suggest that it may underlie the dynamics of a significant number of gene-rich domains in mammals, thus contributing to genome evolution. Finally, using an original model derived from polymer physics, we show that this modulation can be understood as a fundamental helix shape that chromatin tends to adopt in gene-rich domains when no significant locus-specific interaction takes place. CONCLUSIONS: Altogether, our work unveils a fundamental aspect of chromatin dynamics in mammals and contributes to a better understanding of genome organization within chromosomal territories.

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