Alarmone ppGpp directly inhibits tRNA-modifying enzyme MnmE in Bacillus subtilis, affecting biofilm

Researchers reported in Science Advances that the alarmone guanosine tetraphosphate (ppGpp) directly inhibits MnmE (TrmE), a conserved GTPase that modifies tRNA. The enzyme is required for methylaminomethyl (mnm) modification of wobble uridine doi.orgScience Advancesdoi.orgOpen source ↗. The work links bacterial stress signaling to codon-specific translational control doi.orgScience Advancesdoi.orgOpen source ↗.

Using high-resolution ribosome profiling in Bacillus subtilis, the authors found that loss of MnmE selectively increases ribosome pausing at AAG codons. It also reprograms translation of a subset of genes, including small open reading frames doi.orgScience Advancesdoi.orgOpen source ↗.

Among them is a previously unrecognized AAG-containing leader peptide that controls expression of the biofilm repressor AbrB doi.orgScience Advancesdoi.orgOpen source ↗. Consistent with this, mnmE mutants produce extracellular matrix constitutively and bypass the biofilm defect of a relA mutant doi.orgScience Advancesdoi.orgOpen source ↗. The authors describe a pathway connecting ppGpp signaling, tRNA modification, codon-specific translation and multicellular development doi.orgScience Advancesdoi.orgOpen source ↗.