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The aminoacyl-tRNA synthetases are a family of enzymes involved in the process of translation, more specifically, ligating amino acids to their cognate tRNA molecules. Recent evidence suggests that aminoacyl-tRNA synthetases are capable of aminoacylating proteins, some of which are involved in the autophagy pathway. Here, we test the conditions under which E. coli and human threonyl-tRNA synthetases, as well as hisidyl-tRNA synthetase aminoacylate themselves. These reactions are ATP dependent, stimulated by Mg2+, and are inhibited by increasing cognate tRNA concentrations. These data represent the foundation for future aminoacylation experiments, specifically delving into the relationship between the autophagy pathway and the aminoacylation of proteins. Additionally, we provide evidence of the inhibitory abilities of the compound EHTS-0 on both E. coli and human threonyl-tRNA synthetases. Further, we also show that an EHTS-0 analog, EHTS-1, also significantly inhibits E. coli threonyl-tRNA synthetase but not the human enzyme. These data could be useful in determining the potential for EHTS-0 and EHTS-1 as possibly anti-angiogenic drugs.

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Despite the high mortality rate of ovarian cancer, there are few selective biomarkers that detect its progression and none have become successful targets for therapy. A complex microenvironment that promotes angiogenesis, reduces immune responses and alters the integrity of the surrounding matrix is involved through the biology of ovarian cancer. Previous studies done by our lab and collaborators indicated that extracellular threonyl-tRNA synthetase (TARS) is a pro-angiogenic mediator of the ovarian tumor microenvironment, which is secreted in response to inflammatory signals, and actively promotes angiogenesis. In order to better understand the mechanisms underlying the angiogenic effects of TARS in ovarian cancer, it is essential to identify whether it directly affects ovarian tumor growth and invasion. Preliminary evidence indicated that TARS is secreted from ovarian cancer cells in response to TNF-α and TARS exhibits extracellular angiogenic activity. In previous studies, TARS was shown to significantly increase migration of HUVECs in a transwell assay to an extent that was similar to VEGF. The purpose of this project was to establish a role for TARS in tumor progression and its potential as a diagnostic marker using an animal model of ovarian cancer. The hypothesis tested is that TARS plays a key role in the angiogenic and invasive potential of ovarian cancer, and TARS inhibition will reduce the angiogenic effect of tumor cells which is reflected by measurement of intratumor microvessel density (MVD). The study tested the effect of BC194-mediated TARS inhibition on the development of ovarian tumors in ID8 mouse model. We found a positive correlation between TARS expression and ovarian cancer progression, and TARS inhibition with BC194 reduce the progression of ovarian cancer. These data suggest that TARS has an important role in the tumor microenvironment and that TARS inhibition should be further investigated as a therapy for ovarian and other angiogenic cancers.

The protein Liquid facets (Lqf) promotes endocytosis at the plasma membrane1. Lqf activity is required for proper Notch signaling, likely through facilitating the endocytosis of Notch ligand by indirectly linking ligand to clathrin. A genetic modifier screen to identify genes that interact with lqf was performed by a previous graduate student. Genes identified in the screen might provide new insights into how Lqf promotes endocytosis or how Notch signaling is regulated. In this work, I performed genetic mapping techniques to identify the genes mutated in each complementation group of the screen. I identified the gene mutated in complementation group 6 as mitochondrial alanyl tRNA synthetase (Aats-ala-m). tRNA synthetases link a tRNA to its cognate amino acid during translation. Mitochondrial tRNA synthetases function in the mitochondria in translation. Aats-ala-m genetically interacts with lqf, suggesting the two genes function in the same pathway. In this work, I also identified chromosomal regions where the genes mutated in complementation groups 1,2, and 9 are located. / text

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