Poster abstracts
Poster number 84 submitted by Antigone Wilson
Investigating structural and functional elements critical for complex formation between the SreA riboswitch and prfA thermosensor
Antigone N. Wilson (Department of Chemistry, University of Michigan), Martin OSteen (Program in Biophysics, University of Michigan), Jocelyn V. Chen (Department of Chemistry, University of Michigan), Aldrex Munsayac (Department of Chemistry, University of Michigan), Sarah C. Keane (Program in Biophysics & Department of Chemistry, University of Michigan)
Abstract:
Riboswitches are regulatory RNA elements that typically act in cis, controlling expression of their downstream gene in response to a cognate ligand. Interestingly, in Listeria monocytogenes, a saprophyte and opportunistic foodborne pathogen, an S-adenosylmethionine (SAM) riboswitch was previously reported to have a non-canonical trans regulatory role through interaction with an RNA thermosensor (RNAT). The RNAT precedes the mRNA that encodes for Positive Regulatory Factor A (PrfA), the master virulence regulatory protein in L. monocytogenes. SAM riboswitch element A (SreA) was predicted to bind the prfA RNAT and repress translation of the prfA mRNA, even at elevated temperatures, which would affect virulence gene expression. However, we lack a molecular-level understanding of this interaction. Using a toolkit of biochemical and biophysical techniques, including electrophoretic mobility shift assays (EMSAs), small-angle X-ray scattering (SAXS), and in vitro transcription/translation assays, we were able to validate this trans interaction and determine the sequence and structural elements necessary for binding and translation inhibition. We hypothesize that PrfA translational regulation by SreA occurs co-transcriptionally and results from kinetically driven complex formation. Our work highlights the critical role non-coding (nc) RNAs play in bacterial gene regulation and their implications for virulence regulation and metabolism.
Keywords: riboswitch, RNA thermosensor, virulence