3'UTR RNA editing driven by ADAR1 modulates MDM2 expression in breast cancer cells

Area of Science:

• Molecular Biology
• Cancer Research
• Epigenetics

Background:

• Epitranscriptomic modifications, including RNA editing, can alter protein levels of cancer-related genes.
• Adenosine-to-Inosine (A-to-I) RNA editing, catalyzed by ADAR1, is implicated in cancer progression.
• RNA editing in 3' untranslated regions (3'UTRs) influences mRNA stability, localization, and translation.

Purpose of the Study:

• To identify breast cancer-enriched RNA editing sites in silico.
• To investigate the role of ADAR1-mediated RNA editing in 3'UTRs of cancer-related genes.
• To explore the mechanistic interplay between 3'UTR RNA editing and mRNA polyadenylation.

Main Methods:

• In silico analysis of TCGA breast cancer RNA-seq data to detect differential RNA editing sites.
• Confirmation of A-to-I editing in 3'UTRs of MDM2, GINS1, and F11R using RNA immunoprecipitation and ADAR1 knockdown experiments.
• Reporter assays, biotin-based proximity labeling mass spectroscopy, and co-immunoprecipitation to elucidate mechanisms.

Main Results:

• Majority of differential RNA editing events were located in 3'UTRs.
• ADAR1 directly interacts with the 3'UTRs of MDM2, GINS1, and F11R, and mediates their A-to-I editing.
• RNA editing of MDM2 3'UTR enhances protein expression; ADAR1 and CSTF2 knockdown reduces MDM2 protein levels, indicating an interplay with the polyadenylation machinery.

Conclusions:

• ADAR1-dependent 3'UTR RNA editing plays a significant role in regulating MDM2 oncogene expression in breast cancer.
• A novel interplay exists between 3'UTR RNA editing and the mRNA polyadenylation machinery.
• These findings highlight ADAR1's role in cancer-associated RNA editing and suggest its potential as a therapeutic target.