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Method for Measuring the Activity of Deubiquitinating Enzymes in Cell Lines and Tissue Samples
Published on: May 10, 2015
Deubiquitinase USP45 stabilizes RTCB and DDX1, promoting tumorigenesis and chemoresistance
Wen Sun1, Chuncheng Li1, Xiao Tu2
1Key Laboratory of Bio-Resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, 610065, China.
Abstract:
The RNA ligase RTCB and DEAD-box helicase DDX1 regulate critical processes including microRNA maturation and DNA repair, with emerging roles in tumorigenesis and chemoresistance. However, their post-translational regulatory mechanisms remain elusive. Here, we identify the deubiquitinase USP45 as a central coordinator that interacts and co-localizes with RTCB and DDX1. USP45 directly removes polyubiquitin chains from both proteins, thereby stabilizing RTCB and DDX1 in a substrate-specific manner. Notably, USP45-mediated DDX1 deubiquitination requires RTCB, whereas RTCB deubiquitination is DDX1-independent, revealing an asymmetric regulatory hierarchy. Functionally, USP45 cooperates with RTCB and DDX1 to regulate tumor-associated phenotypes in both cellular and murine models, including promoting cell proliferation through RTCB-dependent DDX1 deubiquitination and enhancing chemoresistance through both RTCB- and DDX1-driven pathways. Clinical bioinformatics analyses further reveal that elevated expression of USP45, RTCB, and DDX1 correlates with poor patient survival. Our findings establish the USP45-RTCB-DDX1 axis as a dual driver of oncogenesis and chemoresistance via specific RTCB/DDX1 post-translational stabilization, nominating USP45 inhibition as a therapeutic strategy to suppress cancer progression and overcome treatment resistance.
Insights
The deubiquitinase USP45 stabilizes RNA ligase RTCB and DEAD-box helicase DDX1, promoting cancer cell proliferation and chemoresistance. Inhibiting USP45 may offer a therapeutic strategy against cancer progression and treatment resistance.
Area of Science:
- Molecular Biology
- Cancer Biology
- Biochemistry
Background:
- RNA ligase RTCB and DEAD-box helicase DDX1 are crucial for microRNA maturation and DNA repair.
- Their roles in tumorigenesis and chemoresistance are emerging, but post-translational regulation is unclear.
Purpose of the Study:
- To investigate the post-translational regulation of RTCB and DDX1.
- To identify key regulators involved in cancer progression and chemoresistance.
Main Methods:
- Co-immunoprecipitation and co-localization assays to study protein interactions.
- Ubiquitination and deubiquitination assays to assess USP45 activity.
- Cellular and murine models to evaluate functional roles in proliferation and chemoresistance.
- Bioinformatics analysis of clinical patient data.
Main Results:
- USP45 interacts with and deubiquitinates both RTCB and DDX1, stabilizing them in a substrate-specific manner.
- A regulatory hierarchy exists where RTCB is required for DDX1 deubiquitination by USP45.
- The USP45-RTCB-DDX1 axis promotes cell proliferation and chemoresistance in vitro and in vivo.
- Elevated USP45, RTCB, and DDX1 expression correlates with poor patient survival.
Conclusions:
- USP45 acts as a central coordinator stabilizing RTCB and DDX1, driving oncogenesis and chemoresistance.
- The USP45-RTCB-DDX1 axis represents a novel therapeutic target.
- USP45 inhibition is a potential strategy to combat cancer progression and treatment resistance.
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