Detection and Functional Analysis of SUMO-Modified MEK.

Small ubiquitin-like modifier (SUMO) is a posttranslational protein modifier that binds target proteins covalently (protein sumoylation) and remarkably alters their functions. Protein sumoylation has been linked to various cellular functions such as cell division, DNA repair, and import of nuclear proteins. Thus, its dysregulation is implicated in diverse human diseases such as neurodegenerative disorders and cancers. We recently found that the kinase activity of MEK proteins, which function as central components of the ERK-MAPK cascade and amplify an extracellular proliferation signal, is negatively regulated by sumoylation. Moreover, the oncogenic activity of Ras is enhanced by the abrogation of MEK-sumoylation in cancer cells. Here, we describe several tools and techniques utilized for the elucidation of the properties of SUMO-MEK in our previous reports. We believe that these methods can be used as robust tools for investigating and understanding the biological roles of various SUMO-modified (sumoylated) proteins.