Inhibition of IRES-dependent translation of caspase-2 by HuR confers chemotherapeutic drug resistance in colon carcinoma cells
- HuR plays an important role in tumor cell survival mainly through posttranscriptional upregulation of prominent anti-apoptotic genes. In addition, HuR can inhibit the translation of pro-apoptotic factors as we could previously report for caspase-2. Here, we investigated the mechanisms of caspase-2 suppression by HuR and its contribution to chemotherapeutic drug resistance of colon carcinoma cells. In accordance with the significant drug-induced increase in cytoplasmic HuR abundance, doxorubicin and paclitaxel increased the interaction of cytoplasmic HuR with the 5ʹuntranslated region (5ʹUTR) of caspase-2 as shown by RNA pull down assay. Experiments with bicistronic reporter genes furthermore indicate the presence of an internal ribosome entry site (IRES) within the caspase-2-5ʹUTR. Luciferase activity was suppressed either by chemotherapeutic drugs or ectopic expression of HuR. IRES-driven luciferase activity was significantly increased upon siRNA-mediated knockdown of HuR implicating an inhibitory effect of HuR on caspase-2 translation which is further reinforced by chemotherapeutic drugs. Comparison of RNA-binding affinities of recombinant HuR to two fragments of the caspase-2-5ʹUTR by EMSA revealed a critical HuR-binding site residing between nucleotides 111 and 241 of caspase-2-5ʹUTR. Mapping of critical RNA binding domains within HuR revealed that a fusion of RNA recognition motif 2 (RRM2) plus the hinge region confers a full caspase-2-5ʹUTR-binding. Functionally, knockdown of HuR significantly increased the sensitivity of colon cancer cells to drug-induced apoptosis. Importantly, the apoptosis sensitizing effects by HuR knockdown were rescued after silencing of caspase-2. The negative caspase-2 regulation by HuR offers a novel therapeutic target for sensitizing colon carcinoma cells to drug-induced apoptosis.
Author: | Amel Badawi, Abhiruchi Biyanee, Usman NasrullahORCiDGND, Sofia Winslow, Tobias SchmidORCiDGND, Josef PfeilschifterGND, Wolfgang EberhardtGND |
---|---|
URN: | urn:nbn:de:hebis:30:3-463145 |
DOI: | https://doi.org/10.18632/oncotarget.24840 |
ISSN: | 1949-2553 |
Pubmed Id: | https://pubmed.ncbi.nlm.nih.gov/29719611 |
Parent Title (English): | OncoTarget |
Publisher: | Impact Journals LLC |
Place of publication: | [s. l.] |
Document Type: | Article |
Language: | English |
Year of Completion: | 2018 |
Date of first Publication: | 2018/04/06 |
Publishing Institution: | Universitätsbibliothek Johann Christian Senckenberg |
Release Date: | 2018/08/16 |
Tag: | HuR; IRES translation; caspase-2; chemotherapeutic drug resistance; colon carcinoma cells |
Volume: | 9 |
Issue: | 26 |
Page Number: | 19 |
First Page: | 18367 |
Last Page: | 18385 |
Note: | All site content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 License. |
HeBIS-PPN: | 450643956 |
Institutes: | Medizin / Medizin |
Dewey Decimal Classification: | 6 Technik, Medizin, angewandte Wissenschaften / 61 Medizin und Gesundheit / 610 Medizin und Gesundheit |
Sammlungen: | Universitätspublikationen |
Open-Access-Publikationsfonds: | Medizin |
Licence (German): | Creative Commons - Namensnennung 3.0 |