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.

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Author:Amel Badawi, Abhiruchi Biyanee, Usman Nasrullah, Sofia Winslow, Tobias Schmid, Josef Martin PfeilschifterGND, Wolfgang Eberhardt
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):License LogoCreative Commons - Namensnennung 3.0