Chromatin remodelers are complexes able to both alter histone-DNA interactions and to mobilize nucleosomes. The mechanism of their action and the conformation of remodeled nucleosomes remain a matter of debates. In this work we compared the type and structure of the products of nucleosome remodeling by SWI/SNF and ACF complexes using high-resolution microscopy combined with novel biochemical approaches. We find that SWI/SNF generates a multitude of nucleosome-like metastable particles termed "remosomes". Restriction enzyme accessibility assay, DNase I footprinting and AFM experiments reveal perturbed histone-DNA interactions within these particles. Electron cryo-microscopy shows that remosomes adopt a variety of different structures with variable irregular DNA path, similar to those described upon RSC remodeling. Remosome DNA accessibility to restriction enzymes is also markedly increased. We suggest that the generation of remosomes is a common feature of the SWI/SNF family remodelers. In contrast, the ACF remodeler, belonging to ISWI family, only produces repositioned nucleosomes and no evidence for particles associated with extra DNA, or perturbed DNA paths was found. The remosome generation by the SWI/SNF type of remodelers may represent a novel mechanism involved in processes where nucleosomal DNA accessibility is required, such as DNA repair or transcription regulation.
- MeSH
- adenosintrifosfát metabolismus farmakologie MeSH
- bezbuněčný systém MeSH
- chromozomální proteiny, nehistonové fyziologie MeSH
- DNA bakterií metabolismus MeSH
- DNA footprinting MeSH
- fungální proteiny fyziologie MeSH
- histony genetika metabolismus MeSH
- mikroskopie atomárních sil MeSH
- multiproteinové komplexy fyziologie MeSH
- nukleozomy fyziologie ultrastruktura MeSH
- plazmidy chemie MeSH
- proteiny vázající RNA fyziologie MeSH
- rekombinantní proteiny metabolismus MeSH
- restrikční endonukleasy typu II MeSH
- restrukturace chromatinu genetika fyziologie MeSH
- Saccharomyces cerevisiae metabolismus ultrastruktura MeSH
- Xenopus laevis genetika MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Chromatin adopts a diversity of regular and irregular fiber structures in vitro and in vivo. However, how an array of nucleosomes folds into and switches between different fiber conformations is poorly understood. We report the 9.7 Å resolution crystal structure of a 6-nucleosome array bound to linker histone H1 determined under ionic conditions that favor incomplete chromatin condensation. The structure reveals a flat two-start helix with uniform nucleosomal stacking interfaces and a nucleosome packing density that is only half that of a twisted 30-nm fiber. Hydroxyl radical footprinting indicates that H1 binds the array in an on-dyad configuration resembling that observed for mononucleosomes. Biophysical, cryo-EM, and crosslinking data validate the crystal structure and reveal that a minor change in ionic environment shifts the conformational landscape to a more compact, twisted form. These findings provide insights into the structural plasticity of chromatin and suggest a possible assembly pathway for a 30-nm fiber.
- MeSH
- DNA chemie genetika metabolismus MeSH
- elektronová kryomikroskopie MeSH
- Escherichia coli genetika metabolismus MeSH
- exprese genu MeSH
- genetické vektory chemie metabolismus MeSH
- histony chemie genetika metabolismus MeSH
- hydroxylový radikál chemie MeSH
- interakční proteinové domény a motivy MeSH
- klonování DNA MeSH
- konformace proteinů, alfa-helix MeSH
- konformace proteinů, beta-řetězec MeSH
- krystalografie rentgenová MeSH
- lidé MeSH
- molekulární modely MeSH
- multimerizace proteinu MeSH
- nukleozomy chemie metabolismus ultrastruktura MeSH
- osmolární koncentrace MeSH
- protein 1 vytvářející nukleozómy chemie genetika metabolismus MeSH
- rekombinantní proteiny chemie genetika metabolismus MeSH
- vazba proteinů MeSH
- vazebná místa MeSH
- Xenopus laevis MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
