ArgRS, MetRS, and SRRM2 dependent changes in mRNA splicing and exon usage

Arginine is involved in inflammation and amino acid signaling, in part through the mTORC1 pathway. In cell-based assays and in the mouse, we found that arginine regulates nuclear levels of arginyl-tRNA synthetase (ArgRS) and that nuclear ArgRS interacts and co-localizes with the Serine/Arginine Repetitive Matrix Protein 2 (SRRM2), a spliceosomal protein crucial for the formation of nuclear speckle condensates. Arginine depletion or ArgRS knock down, both of which decreased nuclear ArgRS levels, mobilized SRRM2 for trafficking from nuclear condensates and altered mRNA processing and splice junction usage while minimally affecting expression of other cellular RNAs. These splice junction changes included a subset that were inversely correlated with SRRM2 knock down induced changes and the affected genes encompassed components of the mTORC1 pathway. This inverse correlation suggests that the nuclear ArgRS-SRRM2 interaction regulates SRRM2 nuclear trafficking and alternative splicing in the physiological response to changed arginine levels resulting from inflammation. Overall design: RNAseq of HepG2 cells expressing either a shSCR control or an shRNA against RARS1 or an shRNA against MARS1 or an shRNA against SRRM2