Chromatin remodelers are ATP-dependent enzymes that reorganize nucleosomes within all eukaryotic genomes. Here we report a complex of the Chd1 remodeler bound to a nucleosome in a nucleotide-free state, determined by cryo-EM to 2.3 Å resolution. The remodeler stimulates the nucleosome to absorb an additional nucleotide on each strand at two different locations: on the tracking strand within the ATPase binding site and on the guide strand one helical turn from the ATPase motor. Remarkably, the additional nucleotide on the tracking strand is associated with a local transformation toward an A-form geometry, explaining how sequential ratcheting of each DNA strand occurs. The structure also reveals a histone-binding motif, ChEx, which can block opposing remodelers on the nucleosome and may allow Chd1 to participate in histone reorganization during transcription.
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http://dx.doi.org/10.1038/s41594-021-00719-x | DOI Listing |
bioRxiv
December 2024
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA USA.
The nucleosome remodeler Chd1 is required for the re-establishment of nucleosome positioning in the wake of transcription elongation by RNA Polymerase II. Previously, we found that Chd1 occupancy on gene bodies depends on the Rtf1 subunit of the Paf1 complex in yeast. Here, we identify an N-terminal region of Rtf1 and the CHCT domain of Chd1 as sufficient for their interaction and demonstrate that this interaction is direct.
View Article and Find Full Text PDFMol Cell
September 2024
School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China. Electronic address:
In this issue of Molecular Cell, Engeholm et al. present cryo-EM structures of the chromatin remodeler Chd1 bound to a hexasome-nucleosome complex, an intermediate state during transcription either with or without FACT to restore the missing H2A-H2B dimer. These two binding modes reveal how Chd1 and FACT cooperate in nucleosome re-establishment during transcription.
View Article and Find Full Text PDFMol Cell
September 2024
Max Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, Göttingen 37077, Germany; Harvard Medical School, Blavatnik Institute, Department of Cell Biology, 240 Longwood Avenue, Boston, MA 02115, USA. Electronic address:
To maintain the nucleosome organization of transcribed genes, ATP-dependent chromatin remodelers collaborate with histone chaperones. Here, we show that at the 5' ends of yeast genes, RNA polymerase II (RNAPII) generates hexasomes that occur directly adjacent to nucleosomes. The resulting hexasome-nucleosome complexes are then resolved by Chd1.
View Article and Find Full Text PDFBiochem Soc Trans
October 2024
School of Life and Environmental Sciences, University of Sydney, Darlington, NSW 2006, Australia.
Chromatin remodelling enzymes reposition nucleosomes throughout the genome to regulate the rate of transcription and other processes. These enzymes have been studied intensively since the 1990s, and yet the mechanism by which they operate has only very recently come into focus, following advances in cryoelectron microscopy and single-molecule biophysics. CHD4 is an essential and ubiquitous chromatin remodelling enzyme that until recently has received less attention than remodellers such as Snf2 and CHD1.
View Article and Find Full Text PDFSci Adv
June 2024
Department of Biotechnology, School of Biological Sciences, University of Kashmir, Srinagar, J&K, 190006, India.
The hierarchical chromatin organization begins with formation of nucleosomes, which fold into chromatin domains punctuated by boundaries and ultimately chromosomes. In a hierarchal organization, lower levels shape higher levels. However, the dependence of higher-order 3D chromatin organization on the nucleosome-level organization has not been studied in cells.
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