Deregulation of the pro-apoptotic BH3-only protein BIM accelerates tumorigenesis in various types of cancers. However, little is known about the regulation of BIM in vivo. Since the highly conserved 3’ untranslated region (UTR) of the Bim mRNA is very long (4.2 kb) compared to the coding sequence (0.6 kb), the UTR seems to fulfil an important role in the regulation of BIM expression and hence its pro-apoptotic action.In order to investigate Bim’s mRNA regulation, we co-expressed GFP-Bim3’UTR reporter constructs with the CCCH Zinc Finger protein (ZFP) RNase family. Interestingly, we were able to identify HELZ, a helicase involved in RNA processing, as a stabilizer of Bim mRNA. Furthermore, we are using the Bim-GFP3’UTR reporter cell lines in combination with pooled lentiviral shRNA libraries targeting 15000 genes to identify novel regulators. Preliminary results showed increased GFP expression, indicating the knock down of Bim mRNA destabilisers. In future experiments we will identify and validate the novel regulators of Bim mRNA in vitro and in vivo. Unravelling the role of potential oncogenic or tumour suppressive proteins may allow us to design new target specific therapies for the treatment of chemoresistant tumours.