CSIG-45. RanBPM AS A PARTNER OF STAT5 REGULATES IFN-λ SIGNALING PATHWAY

RanBPM (Ran-binding protein in the microtubule-organizing center, also known as Ranbp9) is a ubiquitous, nucleocytoplasmic protein whose function is poorly understood. RanBPM acts as a multi-modular scaffolding protein, bridging interactions between the cytoplasmic domains of a variety of membrane receptors and their intracellular signaling targets. In glioma rapid increases in the tyrosine phosphorylation of signal transducers and activators of transcription 5 (STAT5) proteins have been extensively documented in cells stimulated with cytokines and growth factors. However, the mechanisms by which STAT5 translocates to the nucleus and regulates proliferation in human glioblastoma multiforme cells have not been studied in detail. In this study, we are just discussing the interaction of RanBPM and STAT5. To confirm RanBPM as a binding partner of STAT5, GST pull-down and co-immunoprecipitation (Co-IP) assay were applied. And to map the binding site of the two proteins, various truncated plasmids were constructed and these plasmids were transfected with full length gene of RanBPM or STAT5, respectively. To reveal the biological function of RanBPM after interacting with STAT5A, we employed a luciferase reporter linked with a STAT5 binding element to examine the transcriptional activity of STAT5. In the GST pull-down and Co-IP assay, we confirm RanBPM can interact with STAT5. In the binding site experiment, the result revealed that the two domains of RanBPM, RanBPM-N and RanBPM-C were responsible for the linkage with STAT5. And the conserved binding sites of STAT5 take part in this association. In the dual-luciferase assay, the luciferase activity indicated that the overexpression of RanBPM enhanced the transcriptional activity of STAT5 in glioma cells (U87 MG and U251 MG). From these data, we conclude that RanBPM interact with STAT5 and plays a novel role in regulating transcriptional activity of STAT5.