Bottom-up modeling of chromatin segregation due to epigenetic modifications.

Proc Natl Acad Sci U S A

Biophysics Program, Stanford University, Stanford, CA 94305;

Published: December 2018

We use a chromosome-scale simulation to show that the preferential binding of heterochromatin protein 1 (HP1) to regions high in histone methylation (specifically H3K9me3) results in phase segregation and reproduces features of the observed Hi-C contact map. Specifically, we perform Monte Carlo simulations with one computational bead per nucleosome and an H3K9me3 pattern based on published ChIP-seq signals. We implement a binding model in which HP1 preferentially binds to trimethylated histone tails and then oligomerizes to bridge together nucleosomes. We observe a phase reminiscent of heterochromatin-dense and high in H3K9me3-and another reminiscent of euchromatin-less dense and lacking H3K9me3. This segregation results in a plaid contact probability map that matches the general shape and position of published Hi-C data. Analysis suggests that a roughly 20-kb segment of H3K9me3 enrichment is required to drive segregation into the heterochromatic phase.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6294944PMC
http://dx.doi.org/10.1073/pnas.1812268115DOI Listing

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