Tyrosyl-tRNA Synthetase: A Housekeeping Protein and an Attractive Harbinger of Cellular Death

Cytokine-type activities are observed for the human tyrosyl-tRNA synthetase, largely considered as an essential enzyme for protein synthesis, only after cleavage into two fragments. These peptide fragments are novel elements in the orchestration of the tissue response to a cellular suicide program and should be viewed as highly differentiated adaptions of peptide modules with biological activity in more than one kind of environment.