Onero H1

Hong-Zhong Li, Yi Xiao, Qin Li, Jun Yao, Xiangliang Yuan, Yuan Zhang, Xuedong Yin, Yohei Saito, Huihui Fan, Ping Li, Wenling Kuo, Angela P. Halpin, D. Gibbons, H. Yagita, Z. Zhao, D. Pang, G. Ren, C. Yee, J. Lee, Di-Hua Yu

SUMMARY Reinvigoration of anti-tumor immunity remains an unmet challenge. Our retrospective analyses revealed that cancer patients who took antihistamines during immunotherapy treatment had significantly improved survival. We uncovered that histamine and histamine receptor H1 (HRH1) are frequently increased in the tumor microenvironment and induce T cell dysfunction. Mechanistically, HRH1-activated macrophages polarize toward an M2-like immunosuppressive phenotype with increased expression of the immune checkpoint VISTA, rendering T cells dysfunctional. HRH1 knockout or antihistamine treatment reverted macrophages immunosuppression, revitalized T cell cytotoxic function, and restored immunotherapy response. Allergy, via the histamine-HRH1 axis, facilitated tumor growth and induced immunotherapy resistance in mice and humans. Importantly, cancer patients with low plasma histamine levels had more than tripled objective response rate to anti-PD-1 treatment compared to patients with high plasma histamine. Altogether, pre-existing allergy or high histamine levels in cancer patients can dampen immunotherapy responses and warrant prospectively exploring antihistamines as adjuvant agents for combinatorial immunotherapy.

Nevin Yusufova, A. Kloetgen, Matt Teater, Adewola Osunsade, J. Camarillo, Christopher R. Chin, A. Doane, Bryan J. Venters, Stephanie Portillo-Ledesma, Joseph Conway, J. Phillip, O. Elemento, D. Scott, W. Béguelin, J. Licht, N. Kelleher, L. Staudt, A. Skoultchi, Michael-Christopher Keogh, Eftychia Apostolou, C. Mason, M. Imieliński, Tamar Schlick, Yael David, A. Tsirigos, C. Allis, A. Soshnev, E. Cesarman, A. Melnick

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. Mutations in histone H1 induce the remodelling of chromatin architecture to a more relaxed state, which leads to malignant transformation through changes in histone modifications and the expression of stem cell genes.

Michael A. Willcockson, Sean E. Healton, Cary N. Weiss, Boris A. Bartholdy, Yair Botbol, Laxmi N. Mishra, Dhruv S. Sidhwani, Tommy J. Wilson, Hugo B Pinto, Maxim I. Maron, Karin A. Skalina, L. N. Toro, Jie Zhao, Chul-Hwan Lee, Harry Hou, Nevin Yusufova, Cem Meydan, Adewola Osunsade, Yael David, E. Cesarman, A. Melnick, S. Sidoli, B. Garcia, W. Edelmann, F. Macian, A. Skoultchi

H1 linker histones are the most abundant chromatin-binding proteins1. In vitro studies indicate that their association with chromatin determines nucleosome spacing and enables arrays of nucleosomes to fold into more compact chromatin structures. However, the in vivo roles of H1 are poorly understood2. Here we show that the local density of H1 controls the balance of repressive and active chromatin domains by promoting genomic compaction. We generated a conditional triple-H1-knockout mouse strain and depleted H1 in haematopoietic cells. H1 depletion in T cells leads to de-repression of T cell activation genes, a process that mimics normal T cell activation. Comparison of chromatin structure in normal and H1-depleted CD8+ T cells reveals that H1-mediated chromatin compaction occurs primarily in regions of the genome containing higher than average levels of H1: the chromosome conformation capture (Hi-C) B compartment and regions of the Hi-C A compartment marked by PRC2. Reduction of H1 stoichiometry leads to decreased H3K27 methylation, increased H3K36 methylation, B-to-A-compartment shifting and an increase in interaction frequency between compartments. In vitro, H1 promotes PRC2-mediated H3K27 methylation and inhibits NSD2-mediated H3K36 methylation. Mechanistically, H1 mediates these opposite effects by promoting physical compaction of the chromatin substrate. Our results establish H1 as a critical regulator of gene silencing through localized control of chromatin compaction, 3D genome organization and the epigenetic landscape. Experiments using a conditional triple-knockout mouse strain show that histone H1 regulates the activity of chromatin domains by controlling chromatin compaction, genome architecture and histone methylation.

Marco Dombrowski, M. Engeholm, C. Dienemann, S. Dodonova, P. Cramer

Throughout the genome, nucleosomes often form regular arrays that differ in nucleosome repeat length (NRL), occupancy of linker histone H1 and transcriptional activity. Here, we report cryo-EM structures of human H1-containing tetranucleosome arrays with four physiologically relevant NRLs. The structures show a zig-zag arrangement of nucleosomes, with nucleosomes 1 and 3 forming a stack. H1 binding to stacked nucleosomes depends on the NRL, whereas H1 always binds to the non-stacked nucleosomes 2 and 4. Short NRLs lead to altered trajectories of linker DNA, and these altered trajectories sterically impair H1 binding to the stacked nucleosomes in our structures. As the NRL increases, linker DNA trajectories relax, enabling H1 contacts and binding. Our results provide an explanation for why arrays with short NRLs are depleted of H1 and suited for transcription, whereas arrays with long NRLs show full H1 occupancy and can form transcriptionally silent heterochromatin regions. Cryo-EM structures of human H1-containing tetranucleosome arrays with distinct, physiological nucleosome repeat lengths reveal that nucleosomes assume a zig-zag arrangement and H1 binds to stacked nucleosomes with longer linker DNA.

Sarah F. Andrews, Lauren Y Cominsky, Geoffrey D. Shimberg, Rebecca A. Gillespie, J. Gorman, J. Raab, Joshua Brand, A. Creanga, Supra R. Gajjala, S. Narpala, C. S. Cheung, Darcy R. Harris, Tongqing Zhou, Ingelise J. Gordon, Lasonji Holman, Floreliz H. Mendoza, Katherine V. Houser, Grace L. Chen, J. Mascola, B. Graham, P. Kwong, A. Widge, L. Dropulic, J. Ledgerwood, M. Kanekiyo, A. McDermott

Current yearly seasonal influenza vaccines primarily induce an antibody response directed against the immunodominant but continually diversifying hemagglutinin (HA) head region. These antibody responses provide protection against the vaccinating strain but little cross-protection against other influenza strains or subtypes. To focus the immune response on subdominant but more conserved epitopes on the HA stem that might protect against a broad range of influenza strains, we developed a stabilized H1 stem immunogen lacking the immunodominant head displayed on a ferritin nanoparticle (H1ssF). Here, we evaluated the B cell response to H1ssF in healthy adults ages 18 to 70 in a phase 1 clinical trial (NCT03814720). We observed both a strong plasmablast response and sustained elicitation of cross-reactive HA stem–specific memory B cells after vaccination with H1ssF in individuals of all ages. The B cell response was focused on two conserved epitopes on the H1 stem, with a highly restricted immunoglobulin repertoire unique to each epitope. On average, two-thirds of the B cell and serological antibody response recognized a central epitope on the H1 stem and exhibited broad neutralization across group 1 influenza virus subtypes. The remaining third recognized an epitope near the viral membrane anchor and was largely limited to H1 strains. Together, we demonstrate that an H1 HA immunogen lacking the immunodominant HA head produces a robust and broadly neutralizing HA stem–directed B cell response. Description In a phase 1 clinical trial, vaccination with an influenza H1 hemagglutinin stabilized stem nanoparticle elicited a broadly reactive B cell response. Fighting flu A major goal for influenza vaccines is to elicit broadly reactive immune responses that can protect against many strains of the virus. Widge et al. and Andrews et al. report results of a phase 1 clinical trial testing a vaccine that may get closer to this goal. Widge et al. demonstrated that immunization with one or two doses of an H1 hemagglutinin stabilized stem nanoparticle (H1ssF) vaccine was safe in recipients and elicited durable neutralizing antibody responses. Andrews et al. found that memory B cell responses elicited by H1ssF vaccination were broadly cross-reactive and targeted two conserved epitopes on the H1 stem. Together, these studies highlight the potential of H1ssF and similar stem-only immunogens as influenza vaccines. —CM