Additional global approaches based on the yeast proteome microarray (protein array) have led to the identification of over 100 host proteins that interact with viral RNA or the viral replication proteins [25, 26] . Also, proteomics approaches with the highly purified tombusvirus replicase has determined at least seven proteins in the complex, including the viral p33 and p92 pol , the heat shock protein 70 chaperones (Hsp70, Ssa1/2p in yeast), glyceraldehyde-3-phosphate dehydrogenase (GAPDH, encoded by TDH2 and TDH3 in yeast), pyruvate decarboxylase (Pdc1p), Cdc34p ubiquitin conjugating enzyme [14, 26, 27] and eukaryotic translation elongation factor 1A (eEF1A) [25] . The functions of GAPDH and Hsp70 have been studied in some detail [14, 29, 30, 31] , but the roles of the other host proteins, such as eEF1A, in the replicase complex are currently undefined. eEF1A is a highly abundant cellular protein with a role in delivering aminoacyl-tRNA to the elongating ribosome in a GTPdependent manner. Many additional functions have been ascribed to eEF1A including quality control of newly produced proteins, ubiquitin-dependent protein degradation, and organization of the actin cytoskeleton [32, 33] . Although eEF1A has been shown to be part of replicase complexes of several RNA viruses [16, 34, 35, 36] , studies on determining its functions in virus replication are hindered by several major difficulties. These include (i) genetic redundancy: yeast has two eEF1A genes (TEF1 and TEF2), whereas animals and plants have 2-7 genes and several isoforms of eEF1A. (ii) eEF1A provides essential functions for cell viability and mutations could have pleiotropic effects on protein translation, actin bundling and apoptosis. (iii) eEF1A is a very abundant protein that constitutes 1-5% of total cellular proteins, making it difficult to completely remove eEF1A from biochemical assays using cell extracts. (iv) eEF1A is also required for the translation of viral proteins in infected cells, making it difficult to separate its effect on translation versus replication, processes that are interdependent.