Another layer of complexity in Staphylococcus aureus methionine biosynthesis control: Unusual RNase III-driven T-box riboswitch cleavage determines met operon mRNA stability and decay

ABSTRACT: In Staphylococcus aureus, de novo methionine biosynthesis is regulated by a unique hierarchical pathway involving stringent-response controlled CodY repression in combination with a T-box riboswitch and RNA decay. The T-box riboswitch residing in the 5' untranslated region (met leader RNA) of the S. aureus metICFE-mdh operon controls downstream gene transcription upon interaction with uncharged methionyl-tRNA. met leader and metICFE-mdh (m)RNAs undergo RNase-mediated degradation in a process whose molecular details are poorly understood. Here, we determined the secondary structure of the met leader RNA and found the element to harbor, beyond other conserved T-box riboswitch structural features, a terminator helix which is a target for RNase III endoribonucleolytic cleavage. As the terminator is a thermodynamically highly stable structure, it also forms posttranscriptionally in met leader/ metICFE-mdh read-through transcripts. Cleavage by RNase III releases the met leader from metICFE-mdh mRNA and initiates RNase J-mediated degradation of the mRNA from the 5'-end. Of note, metICFE-mdh mRNA stability varies over the length of the transcript with a longer lifespan towards the 3'-end. Corresponding variations in protein levels led us to hypothesize that coordinated RNA decay represents another level in the hierarchical methionine biosynthesis control network to adjust methionine biosynthesis enzyme amounts to current metabolic requirements.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Staphylococcus Aureus (strain Newman)

SUBMITTER: Sandra Maass  

LAB HEAD: Dörte Becher

PROVIDER: PXD022677 | Pride | 2021-02-18

REPOSITORIES: Pride