Abstract A38: In vitro and in vivo interaction of Cdk6 and Eya2 indicate potential crosstalk

Abstract

Abstract We have identified a novel association of the developmentally significant protein, Eya2, with cyclin dependent kinase (cdk) 6. Eya2 is part of the conserved retinal determination network that has been shown to function in fly eye development (Rebay, 2005). In mammals, the EYA gene product has been implicated in gonadogenesis, myogenesis, neurognenesis, limb formation, thymus, and kidney development, in part through its ability to regulate cell proliferation (Zhang 2005). Eya2 is overexpressed in several types of cancers including epithelial ovarian (Zhang et al, 2005), cervical (Bierkens et al, 2013), lung adenocarcinoma (Guo et al, 2009), breast and hematopoietic (Patrick, 2013, Wang, 2011). Cdk6 knockout mice display defects in hematopoiesis, including decreased cellularity of the thymus, red blood cells and lymphocytes (Malumbres, 2004). Cdk6 kinase activity is required for thymocyte development (Hu et al, 2011) and this role is partially mediated by modulating Notch target gene expression. The interaction of these two proteins, each important in both development and cancer, and both involved in regulation of cell proliferation and transcription, was first identified in a yeast two-hybrid analysis of a human fetal brain library. Subsequent results from our labs confirm the association of cdk6 and Eya2 in GST binding assays and co-immunoprecipitations. GST binding assays demonstrated that Six4, a cofactor of Eya2, competes with cdk6 for Eya2 binding. Co-immunoprecipitation of transfected cell lysates and native immunoprecipitations also demonstrate binding. Finally, co-expression of cdk6 with Eya2 reduces the half-life of the Eya2 protein in cell lysates. We propose that cdk6 and Eya2 interact to affect the function of cell proliferation and differentiation that is crucial to both the biology of cancer and development. This interaction could provide a mechanism to allow the expansion of the progenitor cell population prior to differentiation.