TY  - JOUR
A1  - Winkler, Christoph
A1  - Doller, Anke
A1  - Imre, Gergely
A1  - Badawi, Amel
A1  - Schmid, Tobias
A1  - Schulz, Sebastian
A1  - Steinmeyer, Nico
A1  - Pfeilschifter, Josef
A1  - Rajalingam, Krishnaraj
A1  - Eberhardt, Wolfgang
T1  - Attenuation of the ELAV1-like protein HuR sensitizes adenocarcinoma cells to the intrinsic apoptotic pathway by increasing the translation of caspase-2L
T2  - Cell death and disease
N2  - Caspase-2 represents the most conserved member of the caspase family, which exhibits features of both initiator and effector caspases. Using ribonucleoprotein (RNP)-immunoprecipitation assay, we identified the proapoptotic caspase-2L encoding mRNA as a novel target of the ubiquitous RNA-binding protein HuR in DLD-1 colon carcinoma cells. Unexpectedly, crosslinking-RNP and RNA probe pull-down experiments revealed that HuR binds exclusively to the caspase-2-5' untranslated region (UTR) despite that the 3' UTR of the mRNA bears several adenylate- and uridylate-rich elements representing the prototypical HuR binding sites. By using RNAi-mediated loss-of-function approach, we observed that HuR regulates the mRNA and in turn the protein levels of caspase-2 in a negative manner. Silencing of HuR did not affect the stability of caspase-2 mRNA but resulted in an increased redistribution of caspase-2 transcripts from RNP particles to translational active polysomes implicating that HuR exerts a direct repressive effect on caspase-2 translation. Consistently, in vitro translation of a luciferase reporter gene under the control of an upstream caspase-2-5'UTR was strongly impaired after the addition of recombinant HuR, whereas translation of caspase-2 coding region without the 5'UTR is not affected by HuR confirming the functional role of the caspase-2-5'UTR. Functionally, an elevation in caspase-2 level by HuR knockdown correlated with an increased sensitivity of cells to apoptosis induced by staurosporine- and pore-forming toxins as implicated by their significant accumulation in the sub G1 phase and an increase in caspase-2, -3 and poly ADP-ribose polymerase cleavage, respectively. Importantly, HuR knockdown cells remained insensitive toward STS-induced apoptosis if cells were additionally transfected with caspase-2-specific siRNAs. Collectively, our findings support the hypothesis that HuR by acting as an endogenous inhibitor of caspase-2-driven apoptosis may essentially contribute to the antiapoptotic program of adenocarcinoma cells by HuR.
Y1  - 2014
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/42003
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-420035
VL  - 5
IS  - e1321
ER  -