Investigation of IRF4-MEF2D protein-protein interaction in melanoma cells

Abstract

Cancer is a leading cause of death worldwide. Protein-protein interactions (PPIs) constitute a fundamental unit of the oncogenic signaling pathways that stimulate survival, growth and proliferation of cancer cells. Therefore, characterization of PPIs in cancer can help in understanding oncogenic mechanisms and shed the light on possible therapeutic targets. Interferon regulatory factor 4 (IRF4) is a transcription factor that highly depends on PPIs to bind DNA and execute its function. For a long time, IRF4 was thought to be lymphoid speci c protein, limiting the discovery of its interaction partners to immune cells. On the contrary, IRF4 is expressed in other cell lines including melanocytes and melanoma cells. Several genome wide association studies linked IRF4 genotypes with pigmentation phenotypes and the risk of developing melanoma tumors. Despite that, the role of IRF4 in melanoma cells is poorly understood. Due to its dependency on PPIs, one of the main approaches to understand its role in melanoma is identifying its interaction partners. Previous observations in our group pointed towards MEF2D as a potential partner of IRF4 in melanoma. The purpose of this study was to investigate the interaction between IRF4 and MEF2D in melanoma cells and to determine if this interaction is critical for the tumorigenic characteristics of melanoma cells. Using computational prediction algorithms. IRF4-MEF2D PPI was found to be physically plausible. This was followed by co-immunoprecipitation (co-IP) experiments, proximity ligation assay (PLA) experiments and chromatin immunoprecipitation analysis. PLA experiments point toward an IRF4-MEF2D PPI in melanoma cells although further veri cations are warranted. In addition, preliminary phenotypic assays, including trypan blue exclusion and GFP competition assays, indicated that MEF2D itself may play a signi cant role in melanoma cells.