PT  - JOURNAL ARTICLE
AU  - Zhi Yang Tan
AU  - Shujun Cai
AU  - Alex J. Noble
AU  - Jon K. Chen
AU  - Jian Shi
AU  - Lu Gan
TI  - Heterogeneous non-canonical nucleosomes predominate in yeast cells in situ
AID  - 10.1101/2021.04.04.438362
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.04.04.438362
4099  - http://biorxiv.org/content/early/2021/04/04/2021.04.04.438362.short
4100  - http://biorxiv.org/content/early/2021/04/04/2021.04.04.438362.full
AB  - Nuclear processes depend heavily on the organization of chromatin, whose subunits are cylinder-shaped complexes called nucleosomes. A subset of mammalian nucleosomes in situ resemble the canonical structure determined in vitro 24 years ago. The structure of nucleosomes in situ is otherwise poorly understood. Here we use cryo-ET and 3-D classification analysis to study the structure of yeast nucleosomes both in vitro and in situ. We show that the class averages of GFP-tagged yeast nucleosomes in vitro resemble canonical nucleosomes, with additional GFP densities. In contrast, none of the class averages of nucleosome-like particles in situ (inside cells) resemble canonical nucleosomes. The heterogeneous nature of the in situ class averages suggests that the intranuclear environment favors multiple conformations. Using the structural observations here and the results of previous genomics and biochemical studies, we propose a model in which the average yeast nucleosome’s DNA is partially detached in situ.Competing Interest StatementThe authors have declared no competing interest.