Characterization of Arginyl-tRNA-protein transferase 1 (ATE1) in melanoma

Introduction

Arginyl-tRNA-protein transferase 1 (ATE1) is responsible for protein arginylation by transferring arginine from arginyl-tRNA to proteins. This modification occur at the N-termini of proteins, which is expected to impact protein half-life. ATE1 modifications were linked with cell migration, autophagy and transformation. While ATE1 modification of actin was shown to be important for cell migration and invasion, ATE1 knock-out MEF exhibit increased tumorigenic potential. Here, we set to determine the role of ATE1 in melanoma development and response to therapy.

Material and method

We performed biochemical, cell biological, coupled with bioinformatics analyses of ATE1 expression and function in melanoma cell lines and patient specimens. Gain and loss-of function studies were performed in culture and related xenografts.

Results and discussion

ATE1 expression was found to be deregulated in 20% of melanoma patient specimens, and inversely correlate with melanoma patient survival. Elevated level of ATE1 mRNA was seen in metastatic compared to primary melanoma samples. Correspondingly, inhibition of ATE1 decreased melanoma migration in culture. Among the key genetic drivers of melanoma, NRAS mutated melanomas were found to express higher levels of ATE1, implying it is contributing to the development of these tumors. Correspondingly, inhibition of ATE1 expression attenuated growth of melanoma in culture, and sensitized melanoma to serum starvation and to chemotherapeutic drugs. Notably, ATE1 inhibition decreased mTORC1 pathway activation and led to synthetic lethality upon mTOR inhibition. Consistent with its higher expression in NRAS mutant melanoma, ATE1 knock-down conferred higher degree of sensitivity to mTOR inhibitors in NRAS- compared to BRAF- mutant melanoma cells. To map specific substrates that may mediate ATE1 function in NRAS melanoma, we designed and screened synthetic peptide array based on bioinformatic analysis. Ongoing studies validate putative substrates, which will be discussed.

Conclusion

Our data establish the importance of ATE1 in growth, migration and response to therapy of NRAS mutant melanomas. Possible mechanisms underlying ATE1 regulation and function will be discussed.