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XB-ART-56167
Elife January 1, 2019; 8

High-resolution and high-accuracy topographic and transcriptional maps of the nucleosome barrier.

Chen Z , Gabizon R , Brown AI , Lee A , Song A , Díaz-Celis C , Kaplan CD , Koslover EF , Yao T , Bustamante C .


Abstract
Nucleosomes represent mechanical and energetic barriers that RNA Polymerase II (Pol II) must overcome during transcription. A high-resolution description of the barrier topography, its modulation by epigenetic modifications, and their effects on Pol II nucleosome crossing dynamics, is still missing. Here, we obtain topographic and transcriptional (Pol II residence time) maps of canonical, H2A.Z, and monoubiquitinated H2B (uH2B) nucleosomes at near base-pair resolution and accuracy. Pol II crossing dynamics are complex, displaying pauses at specific loci, backtracking, and nucleosome hopping between wrapped states. While H2A.Z widens the barrier, uH2B heightens it, and both modifications greatly lengthen Pol II crossing time. Using the dwell times of Pol II at each nucleosomal position we extract the energetics of the barrier. The orthogonal barrier modifications of H2A.Z and uH2B, and their effects on Pol II dynamics rationalize their observed enrichment in +1 nucleosomes and suggest a mechanism for selective control of gene expression.

PubMed ID: 31364986
PMC ID: PMC6744274
Article link: Elife
Grant support: [+]

Species referenced: Xenopus
Genes referenced: h2ac21 h2bc21 nps


Article Images: [+] show captions
References [+] :
Batta, Genome-wide function of H2B ubiquitylation in promoter and genic regions. 2011, Pubmed