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Updated: Jun 10, 2026
10:27
Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
Published on: December 5, 2019
POSH2 is a RING finger E3 ligase with Rac1 binding activity through a partial CRIB domain
Satu Kärkkäinen1, Maarten van der Linden, G Herma Renkema
1Institute of Medical Technology, University of Tampere, Tampere, Finland.
FEBS Letters
|August 11, 2010
Summary
We discovered POSH2, a new protein homologous to POSH, which acts as an E3 ligase. POSH2 interacts with GTP-loaded Rac1, revealing a new binding domain for this interaction.
Area of Science:
- Molecular Biology
- Cell Signaling
- Protein Biochemistry
Background:
- The Plenty of SH3 domains protein (POSH) functions as an E3 ligase and scaffold protein in JNK-mediated apoptosis.
- POSH proteins link Rac1 to downstream signaling pathways.
Purpose of the Study:
- To identify and characterize novel POSH family members.
- To investigate the interaction of POSH2 with Rac1.
Main Methods:
- p21-activated kinase 2 (PAK2) interactor screening to identify POSH2.
- Analysis of protein homology and domain structure.
- Mapping of the interaction domain between POSH2 and Rac1.
Main Results:
- POSH2 was identified and found to be highly homologous to other POSH proteins.
- POSH2 possesses four Src homology 3 (SH3) domains and a RING finger domain, indicating E3 ligase activity.
- POSH2 directly interacts with GTP-bound Rac1.
- The Rac1-binding site on POSH2 was mapped to a novel partial Cdc42/Rac1-interactive binding domain.
Conclusions:
- POSH2 is a novel E3 ligase and a potential regulator of Rac1 signaling.
- The identification of POSH2 expands the known POSH protein family and their roles in cellular processes.
- The newly identified binding domain provides insights into the mechanism of Rac1 regulation by POSH proteins.
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