A Deadly Double Life

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Science  02 Apr 1999:
Vol. 284, Issue 5411, pp. 63-64
DOI: 10.1126/science.284.5411.63

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The human tyrosyl-tRNA synthetase, an enzyme that connects the amino acid tyrosine with its correct tRNA in preparation for protein synthesis, seems to have a totally different function according to Wakasugi and Schimmel, reporting in this issue. In a Perspective on this work, Weiner and Maizels explain that as cells undergo programmed cell death (apoptosis), tyrosyl-tRNA synthetase is secreted and cleaved into two fragments, each with cytokine activity. Weiner and Maizels speculate that the cytokines might encourage phagocytic cells such as macrophages to arrive at the scene of apoptosis and clear up the cell corpses. The authors also discuss the evolution of this dual existence as the EMAPII-like domain is conserved in the tRNA synthetases of bacteria, yeast, and worms.