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Updated: Feb 6, 2026
In Vitro Analysis of E3 Ubiquitin Ligase Function
Published on: May 14, 2021
The E3 ubiquitin ligase HERC1 controls the ERK signaling pathway targeting C-RAF for degradation
Taiane Schneider1, Arturo Martinez-Martinez1, Monica Cubillos-Rojas1
1Departament de Ciències Fisiològiques, IDIBELL, Campus Bellvitge, Universitat de Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain.
Abstract:
The RAF/MEK/ERK cascade is a conserved intracellular signaling pathway that controls fundamental cellular processes including growth, proliferation, differentiation, survival and migration. Aberrant regulation of this signaling pathway has long been associated with human cancers. A major point of regulation of this pathway occurs at the level of the serine/threonine protein kinase C-RAF. Here, we show how the E3 ubiquitin ligase HERC1 regulates ERK signaling. HERC1 knockdown induced cellular proliferation, which is associated with an increase in ERK phosphorylation and in C-RAF protein levels. We demonstrate that overexpression of wild-type C-RAF is sufficient to increase ERK phosphorylation. Experiments with pharmacological inhibitors of RAF activity, or with interference RNA, show that the regulation of ERK phosphorylation by HERC1 is RAF-dependent. Immunoprecipitation, pull-down and confocal fluorescence microscopy experiments demonstrate an interaction between HERC1 and C-RAF proteins. Mechanistically, HERC1 controls C-RAF stability by regulating its polyubiquitylation in a lysine 48-linked chain. In vitro ubiquitylation assays indicate that C-RAF is a substrate of the E3 ubiquitin ligase HERC1. Altogether, we show how HERC1 can regulate cell proliferation through the activation of ERK signaling by a mechanism that affects C-RAF's stability.
Insights
The E3 ubiquitin ligase HERC1 regulates cell proliferation by controlling the stability of C-RAF protein, a key component of the RAF/MEK/ERK signaling pathway. HERC1 knockdown increases C-RAF levels and ERK activity, promoting cell growth.
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Biology
Background:
- The RAF/MEK/ERK pathway is crucial for cellular functions and its dysregulation is linked to cancer.
- C-RAF is a key regulatory point within this signaling cascade.
- Understanding regulators of C-RAF is vital for cancer research.
Purpose of the Study:
- To elucidate the role of the E3 ubiquitin ligase HERC1 in regulating the RAF/MEK/ERK signaling pathway.
- To investigate the mechanism by which HERC1 influences C-RAF and downstream signaling.
- To determine the impact of HERC1 on cell proliferation.
Main Methods:
- HERC1 knockdown and overexpression studies.
- Western blotting to assess ERK phosphorylation and C-RAF levels.
- Pharmacological inhibition and siRNA to confirm RAF dependency.
- Co-immunoprecipitation, pull-down assays, and confocal microscopy to detect protein interactions.
- In vitro ubiquitylation assays.
Main Results:
- HERC1 knockdown led to increased cellular proliferation, ERK phosphorylation, and C-RAF protein levels.
- HERC1 interacts with C-RAF and targets it for polyubiquitylation via lysine 48-linked chains.
- C-RAF is a direct substrate of HERC1's E3 ubiquitin ligase activity.
- HERC1-mediated regulation of ERK signaling is dependent on RAF activity.
Conclusions:
- HERC1 acts as a negative regulator of C-RAF stability, thereby controlling ERK pathway activation.
- HERC1 influences cell proliferation by modulating C-RAF ubiquitylation and stability.
- This study reveals a novel mechanism linking E3 ubiquitin ligases to cancer-associated signaling pathways.
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