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Histone H1 loss drives lymphoma by disrupting 3D chromatin architecture.

ABSTRACT: Linker histone H1 proteins bind to nucleosomes and facilitate chromatin compaction¹, although their biological functions are poorly understood. Mutations in the genes that encode H1 isoforms B-E (H1B, H1C, H1D and H1E; also known as H1-5, H1-2, H1-3 and H1-4, respectively) are highly recurrent in B cell lymphomas, but the pathogenic relevance of these mutations to cancer and the mechanisms that are involved are unknown. Here we show that lymphoma-associated H1 alleles are genetic driver mutations in lymphomas. Disruption of H1 function results in a profound architectural remodelling of the genome, which is characterized by large-scale yet focal shifts of chromatin from a compacted to a relaxed state. This decompaction drives distinct changes in epigenetic states, primarily owing to a gain of histone H3 dimethylation at lysine 36 (H3K36me2) and/or loss of repressive H3 trimethylation at lysine 27 (H3K27me3). These changes unlock the expression of stem cell genes that are normally silenced during early development. In mice, loss of H1c and H1e (also known as H1f2 and H1f4, respectively) conferred germinal centre B cells with enhanced fitness and self-renewal properties, ultimately leading to aggressive lymphomas with an increased repopulating potential. Collectively, our data indicate that H1 proteins are normally required to sequester early developmental genes into architecturally inaccessible genomic compartments. We also establish H1 as a bona fide tumour suppressor and show that mutations in H1 drive malignant transformation primarily through three-dimensional genome reorganization, which leads to epigenetic reprogramming and derepression of developmentally silenced genes.

SUBMITTER: Yusufova N

PROVIDER: S-EPMC7855728 | biostudies-literature |

REPOSITORIES: biostudies-literature

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NSD2 E1099K drives relapse in pediatric acute lymphoblastic leukemia by disrupting 3D chromatin organization.

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Histone 1 deficiency drives lymphomagenesis through disruption of 3D chromatin architecture

Project description:Linker histone H1 proteins bind to nucleosomes and cause chromatin compaction, although little is known about their biological functions. Histone H1 (HIST1H1B-E) mutations are highly recurrent in B-cell lymphomas and are present in solid tumors, but their cancer relevance and mechanism are unknown. Here we report that lymphoma-associated H1 alleles are genetic driver mutations in lymphomas. H1 mutations disrupt their ability to bind or compact chromatin. This causes profound architectural remodeling of the genome characterized by large-scale, yet focal shifts of chromatin from a compacted, to a relaxed state. The degree of decompaction results in distinct epigenetic states, primarily due to gain of histone H3 lysine 36 dimethylation, and/or loss of repressive H3K27 methylation. These changes unlock expression of stem cell genes that are normally silenced during early development. Loss of H1c and H1e alleles in mice conferred enhanced fitness and self renewal properties to germinal center B-cells, ultimately leading to aggressive lymphoma with enhanced repopulating potential. Collectively, our data indicate that H1 proteins are normally required to sequester early developmental genes into architecturally inaccessible genomic compartments. We furthermore establish H1 as a bona fide tumor suppressor, whose mutation drives malignant transformation primarily through three-dimensional genome reorganization, epigenetic reprogramming and aberrant de-repression of developmentally silenced genes.

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