The role of the E3 igase TRIM-25 in the control of caspase-2 translation and its implication for chemotherapy resistance of colon carcinoma cells

• Applicant: Professor Dr. Wolfgang Eberhardt
• Subject Area: Pharmacology ; Cell Biology
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263162954

Colorectal cancer is one of the most common cancers in the western world. Despite current improved treatment options, the occurrence of drug resistance does still limit the efficacy of antitumour treatments. An evasion of apoptotic cell death is thought as a major reason for therapy resistance of cancer cells. Several lines of experimental evidence implicate that a deficiency in the expression of caspase-2 (synonymic: Nedd2 or Ich 1L) expression correlates with drug resistance of various solid tumours supporting the tumoursuppressive function of this evolutionary highly conserved caspase in human carcinomas. In keeping with the known function of caspase-2 to act as a “damage sensor”, we previously reported that drug-induced inhibition of internal ribosome entry segment (IRES)-dependent translation of caspase-2 occurs through an increased caspase-2-5´UTR binding of the ubiquitous RNA binding protein human antigen R (HuR) and confers chemotherapeutic drug resistance in colon carcinoma cells. In comparison to the mechanisms of caspase-2 activation, the control of caspase-2 translation and its possible impact for therapy resistance is only poorly understood. Using RNA affinity chromatography, we have identified the tri-partite motif-containing protein TRIM25 (synonym: estrogen response finger protein, Efp) an E3 ligase as a further caspase-2-5´UTR binding protein which inhibits caspase-2 translation and in turn protects colon carcinoma cells from drug-induced apoptosis. The major emphasis will be put on the identification of IRES -trans -acting factors (ITAFs) as potential targets of TRIM25-dependent ubiquitination. Data from this project part could provide novel information about the functional role of E3 ligases in the control of diverse RNA functions including IRES-dependent translation. Since caspase-2 is known to be controlled by the DNA damage-induced kinases such as ataxia-telangiectasia mutated (ATM) or ATM-/Rad3-related (ATR) kinase, we want to elucidate whether TRIM25 itself is a direct target of ATM and/or ATR-dependent phosphorylation and consequently, is sensitive to pharmacological inhibitors of both mentioned kinases. The second part of the project will emphasize on the functional consequences of caspase-2 suppression by TRIM25 for chemotherapy resistance of human colon carcinoma cells with a particular focus on caspase-2-triggered and chemotherapeutics-induced DNA damage responses including cell cycle arrest and apoptosis. Data from this project help to evaluate potential benefits of targeting TRIM25 for novel tumour therapies and their implementation in current cancer therapy regimen.

• DFG Programme: Research Grants