Abstract 2545: Regulation of NF-YB by miR-485-3p affects TopoisomeraseIIα expression

Abstract

DNA topoisomerase IIα (TopoIIα) is an essential nuclear enzyme. Our teniposide-resistant human leukemic lymphoblastic cells (CEM/VM-1-5) express reduced TopoIIα protein. To determine the role of TopoIIα in drug resistance, previously we knocked down TopoIIα in parental CEM cells by RNAi. Compared to control cells, CEM-siTopoIIα cells are more resistant to etoposide. Our previous work suggested that the transcription factor NF-YB is a negative regulator of TopoIIα, working through the TopoIIα promoter (Morgan and Beck, Mol. Pharmacol 59:203,2001). We have found that NF-YB protein expression is increased in CEM/VM-1-5 cells compared to CEM cells. This suggests that increased NF-YB may be the cause of reduced TopoIIα in CEM/VM-1-5 cells. We asked what causes the up-regulation of NF-YB in CEM/VM-1-5 cells. MicroRNAs are a recently identified group of non-protein coding RNAs that regulate posttranscriptional gene expression. In our previous study, we found by microRNA profiling that hsa-miR-485-3p, is lower in CEM/VM-1-5 cells compared to CEM cells. MicroRNA target prediction programs also reveal that the 3′ UTR of NF-YB harbors a putative miR-485-3p binding site. We hypothesized that hsa-miR-485-3p regulates drug resistance by decreasing NF-YB expression, which in turn negatively regulates TopoIIα expression. We overexpressed miR-485-3p in CEM/VM-1-5 cells and this led to reduced expression of NF-YB and a corresponding upregulation of TopoIIα. To validate the binding of miR-485-3p to NF-YB 3′-UTR, present experiments with HEK293Tcells using luciferase reporters carrying the 3′-UTR of the NF-YB gene are being done to clarify the role of miR-485-3p in this phenomenon. (Supported in part by CA40570 from NCI and in part by UIC) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2545.