TY  - JOUR
A1  - Badawi, Amel
A1  - Biyanee, Abhiruchi
A1  - Nasrullah, Usman
A1  - Winslow, Sofia
A1  - Schmid, Tobias
A1  - Pfeilschifter, Josef
A1  - Eberhardt, Wolfgang
T1  - Inhibition of IRES-dependent translation of caspase-2 by HuR confers chemotherapeutic drug resistance in colon carcinoma cells
T2  - OncoTarget
N2  - 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.
KW  - caspase-2
KW  - colon carcinoma cells
KW  - chemotherapeutic drug resistance
KW  - HuR
KW  - IRES translation
Y1  - 2018
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/46314
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-463145
SN  - 1949-2553
N1  - All site content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 License.
VL  - 9
IS  - 26
SP  - 18367
EP  - 18385
PB  - Impact Journals LLC
CY  - [s. l.]
ER  -