RT Journal Article
SR Electronic
T1 Nucleosome conformational variability in solution and in interphase nuclei evidenced by cryo-electron miocroscopy of vitreous sections
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 295691
DO 10.1101/295691
A1 Mikhail Eltsov
A1 Diana Grewe
A1 Nicolas Lemercier
A1 Achilleas Frangakis
A1 Françoise Livolant
A1 Amélie Leforestier
YR 2018
UL http://biorxiv.org/content/early/2018/04/06/295691.abstract
AB In Eukaryotes, DNA is wound around the histone core octamer to form the basic chromatin unit, the nucleosome. Atomic resolution structures have been obtained from crystallography and single particle cryo-electron microscopy of identical engineered particles. But native nucleosomes are dynamical entities with diverse DNA sequence and histone content, and little is known about their conformational variability, especially in the cellular context. Using cryo-electron microscopy and tomography of vitreous sections we analyse the conformation of native nucleosomes, both in vitro, using purified particles solubilised at physiologically relevant concentrations (25-50 %), and in situ, within interphase nuclei. We visualise individual nucleosomes at a level of detail that allows us to analyse the conformation of the DNA wrapped around, and measure the distance between the DNA gyres. We evidence a variety of conformations. In interphase nuclei open nucleosomes predominate, with an average inter-gyre distance larger than that of the canonical particle. In concentrated solutions, we evidence a salt–dependant transition, with high salt compact conformations resembling the canonical nucleosome, and open low salt ones, closer to nuclear nucleosomes. Although further particle characterisation and cartography are needed to understand the relationship between this conformational variability and chromatin functional states, this work opens a route to chromatin exploration in situ.