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Retinoid-modulated MAT1 ubiquitination and CAK activity
Qiaojun He1, Hui Peng, Steven J Collins
1Department of Pathology, University of Southern California Keck School of Medicine, Los Angeles, California 90027, USA.
Summary
Retinoic acid (RA) triggers the degradation of menage a trois 1 (MAT1) protein via ubiquitination, reducing cyclin-dependent kinase (CDK)-activating kinase (CAK) activity. This process is crucial for RA-induced cell differentiation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Human cyclin-dependent kinase (CDK)-activating kinase (CAK) regulates cell cycle and differentiation.
- Menage a trois 1 (MAT1) protein assembles CAK and dictates its substrate specificity.
- The intracellular regulation of MAT1 controlling CAK activity remains unclear.
Purpose of the Study:
- Investigate the biochemical pathway of MAT1 degradation induced by retinoic acid (RA).
- Determine the relationship between MAT1 degradation and CAK phosphorylation of retinoic acid receptor alpha (RARα).
Main Methods:
- Studied RA-induced HL60 cell proliferation/differentiation (P/D) transition.
- Analyzed MAT1 degradation and CAK phosphorylation of RARα.
- Investigated ubiquitination-proteasome pathway involvement.
Main Results:
- RA induces ubiquitination-proteolysis of MAT1, specifically targeting CAK-free MAT1.
- RA-induced MAT1 ubiquitination reduces CAK abundance and RARα phosphorylation.
- Inhibiting MAT1 ubiquitination counteracted the RA-induced effects.
Conclusions:
- RA induces MAT1 ubiquitination, leading to decreased CAK phosphorylation of RARα.
- MAT1 ubiquitination is a novel mechanism in RA-mediated P/D transition.
- MAT1 ubiquitination may decrease CAK activity, facilitating the switch from proliferation to differentiation.