LAUSR

Gene Expression Most Gram-positive bacteria have genetic switches that regulate the expression of genes involved in amino acid synthesis. These switches are sequences called T-boxes that occur before the coding sequence in the relevant messenger RNAs. They bind to specific transfer RNA (tRNA) and, if it is charged with amino acid, suppress expression of the messenger RNA. Three papers—by Li et al. , Battaglia et al. , and Suddala and Zhang, with an overview provided by Weaver and Serganov—describe the structures of different classes of T-boxes bound to tRNA. The structures show differences in anticodon recognition that ensure specific binding. The papers differ in their interpretations of how expression is inhibited when the tRNA is charged with amino acid. Nat. Struct. Mol Biol. 26 , 1094, 1106, 1114, 1081 (2019).