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MicroRNA (miRNA)-to-miRNA Regulation of Programmed Cell Death 4 (PDCD4)
Pamela Ajuyah1, Meredith Hill2, Alireza Ahadi2
1School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney, NSW, Australia.
Abstract:
The regulation of tumor suppressor genes by microRNAs (miRNAs) is often demonstrated as a one-miRNA-to-one-target relationship. However, given the large number of miRNA sites within a 3' untranslated region (UTR), most targets likely undergo miRNA cooperation or combinatorial action. Programmed cell death 4 (PDCD4), an important tumor suppressor, prevents neoplastic events and is commonly downregulated in cancer. This study investigates the relationship between miRNA 21 (miR-21) and miR-499 in regulating PDCD4. This was explored using miRNA overexpression, mutational analysis of the PDCD4 3' UTR to assess regulation at each miRNA site, and 50% inhibitory concentration (IC50) calculations for combinatorial behavior. We demonstrate that the first miR-499 binding site within PDCD4 is inactive, but the two remaining sites are both required for PDCD4 suppression. Additionally, the binding of miR-21 to PDCD4 influenced miR-499 activity through an increase in its silencing potency and stabilization of its mature form. Furthermore, adjoining miRNA sites more than 35 nucleotides (nt) apart could potentially regulate thousands of 3' UTRs, similar to that observed between miR-21 and miR-499. The regulation of PDCD4 serves as a unique example of regulatory action by multiple miRNAs. This relationship was predicted to occur on thousands of targets and may represent a wider mode of miRNA regulation.
Insights
MicroRNAs (miRNAs) exhibit complex regulation of tumor suppressors like PDCD4. This study reveals miR-21 and miR-499 cooperate to suppress PDCD4, suggesting a broader mechanism of miRNA action in cancer.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- MicroRNA (miRNA) regulation of tumor suppressor genes is often viewed as a singular interaction.
- However, combinatorial or cooperative miRNA action on gene targets is increasingly recognized.
- Programmed cell death 4 (PDCD4) is a crucial tumor suppressor frequently downregulated in various cancers.
Purpose of the Study:
- To investigate the cooperative regulatory relationship between microRNA-21 (miR-21) and microRNA-499 (miR-499) on the tumor suppressor gene PDCD4.
- To elucidate the specific roles of individual miRNA binding sites within the PDCD4 3' untranslated region (UTR).
- To explore the impact of miR-21 on miR-499 activity and PDCD4 suppression.
Main Methods:
- Utilized miRNA overexpression and mutational analysis of the PDCD4 3' UTR.
- Assessed miRNA binding site functionality and regulatory contributions.
- Performed 50% inhibitory concentration (IC50) calculations to evaluate combinatorial effects.
Main Results:
- The first miR-499 binding site on PDCD4 was found to be inactive; two other sites were essential for PDCD4 suppression.
- miR-21 binding to PDCD4 enhanced miR-499's silencing efficacy and stabilized its mature form.
- Cooperative regulation was observed between miR-21 and miR-499, impacting PDCD4 levels.
Conclusions:
- The regulation of PDCD4 by miR-21 and miR-499 exemplifies a multi-miRNA cooperative mechanism.
- This cooperative action, even with sites >35 nucleotides apart, may be a widespread mode of gene regulation.
- This finding has implications for understanding miRNA-mediated gene control in cancer and other diseases.
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