Related Experiment Video
Updated: Sep 9, 2025

In Vitro Analysis of E3 Ubiquitin Ligase Function
Published on: May 14, 2021
Catalytic pocket of Clr4 (Suv39h) methyltransferase serves as a substrate receptor for Cullin 4-dependent histone H3
Katarina Psenakova1,2, Swapnil S Parhard1, Joao A Paulo3
1Howard Hughes Medical Institute, Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA.
Abstract:
Histone H3 lysine 9 (H3K9) methylation must be regulated to prevent inappropriate heterochromatin formation. Regulation of the conserved fission yeast H3K9 methyltransferase Clr4 (Suv39h) involves an automethylation-induced conformational switch and interaction of its catalytic SET domain with mono-ubiquitinated histone H3 lysine 14 (H3K14ub), a modification catalyzed by the Cul4 subunit of the CLRC complex. Using reconstituted CLRC, we show that Clr4 catalytic pocket serves as a substrate receptor for Cul4-dependent H3K14 ubiquitination. H3K14ub activates Clr4 to catalyze cis methylation of H3K9 on the same histone tail, while Clr4 automethylation enables H3K14ub-bound Clr4 to methylate H3K9 on an unmodified H3 tail in trans. Crosslinking and structural modeling reveal interactions between Clr4 chromo and SET domains, and between the chromodomain and H3K14ub, suggesting that the chromodomain reads H3K9me3 and H3K14ub to allosterically regulate Clr4 activity. H3K14 ubiquitination therefore regulates Clr4 by promoting its recruitment and by positioning H3K9 in the active site.
Related Concept Videos
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein....
Regulated Protein Degradation
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Export of Misfolded Proteins out of the ER
Anaphase Promoting Complex
The Proteasome
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
Receptor Downregulation in MVBs
The EGFR can initiate signaling pathways that lead to cell proliferation, migration, and differentiation. Overexpression of EGFR stimulates cells to proliferate. Excessive EGFR...

