Lysyl-tRNA synthetase (LysRS) was found to produce diadenosine tetraphosphate (Ap4A) in vitro more than two decades ago. Here, we used LysRS silencing in mast cells in combination with transfected normal and mutated LysRS to demonstrate in vivo the critical role played by LysRS in the production of Ap4A in response to immunological challenge. Upon such challenge, LysRS was phosphorylated on serine 207 in a MAPK-dependent manner, released from the multisynthetase complex, and translocated into the nucleus. We previously demonstrated that LysRS forms a complex with MITF and its repressor Hint-1, which is released from the complex by its binding to Ap4A, enabling MITF to transcribe its target genes. Here, silencing LysRS led to reduced Ap4A production in immunologically activated cells, which resulted in a lower level of MITF inducible genes. Our data demonstrate that specific LysRS serine 207 phosphorylation regulates Ap4A production in immunologically stimulated mast cells, thus implying that LysRS is a key mediator in gene regulation.
Bibliographical noteFunding Information:
This work was supported by the United States Binational Science Foundation (E.R., 2003-009); the Israeli Academy of Science (E.R., 144/04); the German-Israel Foundation for Scientific Research and Development (E.R., I-726-10.2); the Morasha Foundation Fund (H.N.); the Acceleration Research of KOSEF (S.K., 2009-0063498); and the 21st Frontier Functional Proteomics Research (S.K., FPR0881-250). I.C.-L. was supported by the Canadian Friends of Hebrew University. We would like to thank Dr. Mario Lebendiker from The Protein Purification Facility, Wolfson Centre for Applied Structural Biology, Hebrew University of Jerusalem, for his help in gel filtration chromatography.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology