The Impact of EVI1 on Carbonic Anhydrase III Expression and the Sensitivity of Rat1 Fibroblasts to H2O2-induced Apoptosis

EVI1 is a transcriptional factor with two distinct zinc finger domains and encoded in human chromosome 3q26. In human, the protein is believed to have role in cell proliferation, organogenesis and it was detected in kidneys and lungs. EVI1 overexpression has been associated with various conditions such as myelodysplastic syndrome (MDS), juvenile myelomonocytic leukaemia (JMML) and acute myeloid leukaemia (AML). In the present study, Carbonic Anhydrase III (CaIII) was expressed at much lower levels in EVI1 overexpressing fibroblast cells compared to the wild type indicating an inhibitory role of EVI1 against CaIII. Our results were further confirmed by western blot in which CaIII protein in normal fibroblast cells was more abundance than that in cells with EVI1 enforced expression. Furthermore, Luciferase reporter assay showed repressed promotor activity in EVI1 overexpressing cells resulted from EVI1 interfering with CaIII promotor by direct or indirect binding. Fibroblast cells with repressed CaIII showed higher sensitivity to apoptosis induced by hydrogen peroxide, this is attributed to the downregulation of CaIII gene which has a defensive role against the oxidative damage. It has been reported that the CaIII overexpression increases the cell resistance against the oxidative stress caused by exposure to H2O2. Thus, elevated EVI1 levels repress CaIII expression leading to increased cell sensitivity to H2O2-induced apoptosis. These findings seem to be constant with previous studies, and might introduce a novel approach to treat leukaemia depending on H2O2-induced apoptosis.