Acknowledgements: We are grateful to members of the Labib laboratory for invaluable advice on recombinant protein purification and C. elegans techniques, and to members of the Rouse laboratory for fruitful discussion. We thank K. Rasmussen for help with ATAC–seq in human cells; R. Sundaramoorthy and T. Owen-Hughes (University of Dundee) for the gift of recombinant Xenopus histones; B. Meier and F. Pelisch for help with C. elegans genetics; K. Labib for helpful comments on the manuscript and for the gift of the His6–Ulp1 plasmid; V. Alvarez for help with microscopy and A. Knebel for advice on protein purification. We thank the technical support of the MRC PPU including the DNA Sequencing Service, Tissue Culture team, Reagents and Services team, and the Flow Cytometry & Cell Sorting Facility at the University of Dundee; we thank the (EPI)2 Imaging platform - UMR7216 Epigenetics and Cell Fate centre (Paris) for access to instruments; we also thank N. Wood for help with cloning, and F. Brown and J. Hastie for SPT2 antibody production and purification. We acknowledge the excellent support teams and admin staff in MRC PPU and the School of Life Sciences (University of Dundee) where most of this work was done. This work was supported by the Medical Research Council (grant number MC_UU_00018/5) and the pharmaceutical companies supporting the Division of Signal Transduction Therapy Unit (Boehinger‐Ingelheim, GlaxoSmithKline and Merck KGaA) (J.R.); the Wellcome Trust (grant number 217170) and the MRC (grant number MR/S021620/1) (J.A.); the Korean Institute for Basic Science (grant number IBS-R022-A2-2023) (A.G. and S.G.M.R.); Cancer Research UK (grant number C13474/A27826) and the Wellcome Trust (grant number 219475/Z/19/Z) (E.A.M.); the European Research Council (grant number ERC-2018-CoG-818625) (S.E.P.); the Medical Research Council (grant number MC_UU_00007/15) (C.P.P.); the European Research Council (ERC-2016-StG-715127) (C.A.); the Medical Research Council (grant number MC_U105192715 to L. Passmore). G.S. was supported by an EMBO Long-Term Fellowship (ALTF 951-2018) and a SULSA ECR Development Fund; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 845448 (G.S.). G.F. was supported by an EMBO Long-Term Fellowship (ALTF 1132-2018). P.A. was supported by an EMBO Long-Term Fellowship (ALTF 692–2018). For the purpose of open access, the MRC Protein Phosphorylation and Ubiquitylation Unit has applied a CC BY public copyright license to any Author Accepted Manuscript version arising. The funders had no direct role in study design, data collection and analysis, decision to publish or preparation of the manuscript.Histone chaperones control nucleosome density and chromatin structure. In yeast, the H3-H4 chaperone Spt2 controls histone deposition at active genes but its roles in metazoan chromatin structure and organismal physiology are not known. Here we identify the Caenorhabditis elegans ortholog of SPT2 (CeSPT-2) and show that its ability to bind histones H3-H4 is important for germline development and transgenerational epigenetic gene silencing, and that spt-2 null mutants display signatures of a global stress response. Genome-wide profiling showed that CeSPT-2 binds to a range of highly expressed genes, and we find that spt-2 mutants have increased chromatin accessibility at a subset of these loci. We also show that SPT2 influences chromatin structure and controls the levels of soluble and chromatin-bound H3.3 in human cells. Our work reveals roles for SPT2 in controlling chromatin structure and function in Metazoa
