Chromatin-remodelling ATPases of the Microrchidia (MORC) family regulate gene expression through epigenetic silencing. MORC2, the most frequently mutated MORC protein in cancer and neurological disease, remains poorly characterised mechanistically.
Using in vitro biochemical reconstitution, cryo-electron microscopy, single-molecule biophysics and quantitative mass spectrometry, we present the first comprehensive characterisation of full-length MORC2. We reveal that MORC2 contains multiple DNA-binding sites that undergo conformational changes upon DNA engagement and form a DNA clamp via its C-terminal domain (CTD). The CTD harbours a conserved phosphate-interacting motif that regulates ATP hydrolysis and cooperative DNA binding. Through ATP hydrolysis assays and single molecule DNA compaction assays, we demonstrate that MORC2 remodels chromatin via ATP hydrolysis-dependent DNA compaction, a process dynamically tuned by CTD phosphorylation.
These findings establish CTD phosphorylation as a pivotal regulatory mechanism controlling MORC2's chromatin-silencing activity and provide mechanistic insights into how mutations in this protein contribute to disease pathogenesis.