Purification and biophysical characterization of the AIMP2-DX2 protein.

Besides their primary role in protein synthesis, aminoacyl-tRNA synthetases (AARSs) are involved in several non-canonical processes such as apoptosis, inflammation and angiogenesis through their interactions with various cellular proteins. Nine of these AARSs interact with three aminoacyl-tRNA synthetase interacting multifunctional proteins (AIMPs), forming a multi-synthetase complex (MSC) in eukaryotes. Among the three AIMPs, AIMP2 is involved in controlling cell proliferation and apoptosis. However, a splicing variant of AIMP2 lacking exon 2, referred to as AIMP2-DX2, is oncogenic and compromises the pro-apoptotic activity of AIMP2 by competing with it for p53 and TRAF2. AIMP2-DX2 is also an inhibitor of p14arf activity. Thus, there is a pressing need for structural insight into the oncogenic role of AIMP2-DX2. In this study, we expressed and purified human AIMP2-DX2 using a SUMO tag to more than 95% purity and a yield of 10 mg/L. We have used size exclusion chromatography, glutaraldehyde cross-linking, dynamic light scattering and nuclear magnetic resonance spectroscopy to characterize its biophysical properties. These data indicate monomer-dimer equilibrium of AIMP2-DX2 in solution. These results form the basis for the structure-function study of oncogenic AIMP2-DX2.