Though bacteria in nature are often nutritionally limited and growing slowly, most of our understanding of core cellular processes such as transcription comes from studies in a handful of model organisms doubling rapidly under nutrient-replete conditions. To gain insight into regulators contributing to regulation during growth arrest, we carried out a proteomics-based screen for proteins upregulated by Pseudomonas aeruginosa during growth arrest and identified a small, previously uncharacterized protein which we named SutA. SutA binds RNA polymerase (RNAP), causing widespread changes in gene expression, including upregulation of the ribosomal RNA (rRNA) and other “housekeeping” genes typically highly expressed during growth. These results suggested that SutA might help cells to maintain baseline levels of biosynthetic capacity during extended resource limitation. Next, using biochemical and structural methods, we examined how SutA interacts with RNAP and the functional consequences of these interactions. We find that SutA consists of a central α-helix with unstructured N- and C-terminal tails, and binds to the β1 domain of RNAP. It activates transcription from the P. aeruginosa rrn promoter by both the housekeeping sigma factor holoenzyme (Es70) and the general stress response sigma factor holoenzyme (EsS) in vitro, and its acidic N-terminal tail is required for activation in both holoenzyme contexts. However, we find that the interaction between SutA and each holoenzyme is distinct, with the SutA C-terminal tail and an acidic loop unique to s70 playing the determining roles in these differences. Our results add SutA to a growing list of transcription regulators that use their intrinsically disordered regions to remodel transcription complexes, and lend insight into molecular mechanisms by which an important opportunistic pathogen survives periods of resource limitation.
'Transcriptional regulation during slow growth in Pseudomonas aeruginosa'
Monday, January 21, 2019 - 13:00 to 14:00
CTIR Sir Kenneth and Lady Noreen Murray Seminar Room
Professor Nicola Stanley-Wall
Dr Megan Bergkessel
California Institute of Technology, California