Identification of methylation-dependent biochemical associations of the THO complex

Abstract

Pre-mRNAs must be fully processed and packaged into mature messenger ribonucleoparticles (mRNPs) before being exported to the cytoplasm as fully translatable mRNAs in eukaryotic cells. The intracellular RNA processing steps involved are accomplished through the association of numerous RNA binding proteins (RBPs) such SR proteins with pre-mRNA. The dynamic interactions between the RBPs and the pre-mRNAs suggest that their binding to and dissociation from the RNAs and other proteins may be regulated by the various post-translational modifications contained in the RBPs. One such post-translational modification is the methylation of the arginine residues. In yeast, the enzyme that catalyzes this modification is Hmt1. Some of the known substrates of Hmt1 are Yra1, Hrp1, and Npl3. A major player in facilitating proper mRNP biogenesis is the TREX complex, which is evolutionarily conserved from yeast to humans. The two main constituents of the TREX complex are the stable multi-subunit THO complex and the mRNA transport factors, Sub2 and Yra1. Previous studies have demonstrated the importance of arginine methylation in coordinating certain protein-protein interactions, such as the dissociation of Tho2, a THO complex component, from Npl3 (a mRNA export factor). In this study we investigated changes in methylation-dependent biochemical associations of the THO complex components with the other components of mRNP biogenesis pathway.