Regulated alternative splicing separates canonical and cell signaling functions of aminoacyl-tRNA synthetases

The aminoacyl-tRNA synthetases (aaRS) are ubiquitous and essential enzymes which set the genetic code by attaching amino acids to their cognate tRNAs. Many eukaryotic synthetases balance this key function with diverse roles in cell signaling. Alternative splicing has been proposed as a mechanism whereby aaRS may gain new functionality or be specified from their catalytic role towards alternate activities. Here, I discovered a leukocyte-specific exon-skipping event in human leucyl-tRNA synthetase (LARS) using long-read sequencing. This splice variant, LSV3, lacks all tRNA leucylation activity as skipping of LARS exon 20 causes a 71 amino acid deletion in the catalytic domain. However, LSV3 retains its role as a leucine sensor and signal transducer for the mammalian target of rapamycin (mTOR) pathway, even though the deletion includes a portion of the previously mapped Vps34-binding domain. I further found that expression of LSV3 is regulated by serine-arginine rich splicing factor 1 (SRSF1) in a cell type-specific manner, and this leads to increased exon skipping during immune cell activation and differentiation. Other alternative splicing events related to non-canonical functions of aaRS are controlled by SRSF1, including exon 2 skipping of tryptophanyl-tRNA synthetase (WARS), which induces its anti-angiogenic activity. I also identify a promising new modulator of the cell death inhibition function of glutaminyl-tRNA synthetase (QARS) via skipping of its exon 23. While when this QARS exon 23 skipping increases remains unclear, I found that LARS exon 20 skipping in LSV3 is greatly induced during cell death. Therefore, alternative splicing has provided functional specificity to the housekeeping LARS protein during cell death and immune signaling by separating its canonical and cell signaling roles.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biochemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Baymiller, Maxwell J

Contributors dc:contributor

• Martinis, Susan A
• Chen, Jie
• Chen, Lin-Feng
• Kalsotra, Auinash

• tRNA synthetases
• alternative splicing

Statement dc:rights

• Copyright 2022 Maxwell Baymiller

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115713

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115713