TusA Is a Versatile Protein That Links Translation Efficiency to Cell Division in Escherichia coli

Abstract

To enable accurate and efficient translation, sulfur modifications are introduced posttranscriptionally into nucleosides in tRNAs. The biosynthesis of tRNA sulfur modifications involves unique sulfur trafficking systems for the incorporation of sulfur atoms in different nucleosides of tRNA. One of the proteins that is involved in inserting the sulfur for 5-methylaminomethyl-2-thiouridine (mnm5s2U34) modifications in tRNAs is the TusA protein. TusA, however, is a versatile protein that is also involved in numerous other cellular pathways. Despite its role as a sulfur transfer protein for the 2-thiouridine formation in tRNA, a fundamental role of TusA in the general physiology of Escherichia coli has also been discovered. Poor viability, a defect in cell division, and a filamentous cell morphology have been described previously for tusA-deficient cells. In this report, we aimed to dissect the role of TusA for cell viability. We were able to show that the lack of the thiolation status of wobble uridine (U34) nucleotides present on Lys, Gln, or Glu in tRNAs has a major consequence on the translation efficiency of proteins; among the affected targets are the proteins RpoS and Fis. Both proteins are major regulatory factors, and the deregulation of their abundance consequently has a major effect on the cellular regulatory network, with one consequence being a defect in cell division by regulating the FtsZ ring formation. IMPORTANCE More than 100 different modifications are found in RNAs. One of these modifications is the mnm5s2U modification at the wobble position 34 of tRNAs for Lys, Gln, and Glu. The functional significance of U34 modifications is substantial since it restricts the conformational flexibility of the anticodon, thus providing translational fidelity. We show that in an Escherichia coli TusA mutant strain, involved in sulfur transfer for the mnm5s2U34 thio modifications, the translation efficiency of RpoS and Fis, two major cellular regulatory proteins, is altered. Therefore, in addition to the transcriptional regulation and the factors that influence protein stability, tRNA modifications that ensure the translational efficiency provide an additional crucial regulatory factor for protein synthesis.

A cascade of sulfur transferases delivers sulfur to the sulfur‐oxidizing heterodisulfide reductase‐like complex

“…In Escherichia coli , the three homologous TusA‐family proteins, TusA, YedF, and YeeD have distinct functions and cannot substitute for each other (Dahl et al, 2013 ). Besides contributing to tRNA thiolation (Ikeuchi et al, 2006 ), TusA mediates sulfur transfer for molybdenum cofactor biosynthesis and affects iron–sulfur cluster assembly as well as the activity of major regulatory proteins (Dahl et al, 2013 ; Ishii et al, 2000 ; Yildiz & Leimkühler, 2021 ). YeeD is a component of thiosulfate uptake for sulfur assimilation (Ikei et al, 2024 ; Tanaka et al, 2020 ).…”

TusDCB, a sulfur transferase complex involved in tRNA modification, contributes to UPEC pathogenicity

“…The defect of TusDCB may indirectly affect Fe-S biosynthesis, the other sulfur flow destination, by terminating sulfur flow to tRNA Lys , tRNA Glu and tRNA Gln . Another study showed that Tus proteins contribute to the expression of the global regulators RpoS and Fis 55 . Even though the target of TusDCB's sulfur transfer activity is confined to tRNAs, it is involved in the regulation of diverse physiological functions.…”

New layers of regulation of the general stress response sigma factor RpoS

“…TusA, which is a sulfur-carrying protein that mediates the 2-thiouridine (S 2 U34) wobble-position tRNA modification (Ikeuchi et al, 2006), was shown to be important for the efficient translation of rpoS (Aubee et al, 2017). Another study biochemically confirmed the role of TusA by showing that absence of TusA resulted in decreased translation efficiency of rpoS, through loss of thiolation on Lys, Glu and Gln tRNAs (Yildiz and Leimkühler, 2021). Thus, tRNA modifications and encoding of ORFs with specific codon preference, especially leucine, provide another means of regulation of RpoS, by modulating translational efficiency.…”