Sulfur from Within: Cytosolic tRNA Thiouridinylation.

In this issue of Cell Chemical Biology, Pandey et al. (2018) identified that mitochondrial cysteine desulfurase provides the sulfur species used for tRNA, tRNA, and tRNA thiouridine modification in the cytoplasm. A low-mass sulfur species is exported by the mitochondrial Atm1 transporter and utilized in the thio-modifications.