AUTHOR=Sonnleitner Elisabeth , Bassani Flavia , Cianciulli Sesso Anastasia , Brear Paul , Lilic Branislav , Davidovski Lovro , Resch Armin , Luisi Ben F. , Moll Isabella , Bläsi Udo 

TITLE=Catabolite repression control protein antagonist, a novel player in Pseudomonas aeruginosa carbon catabolite repression control

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1195558

DOI=10.3389/fmicb.2023.1195558

ISSN=1664-302X

ABSTRACT=<p>In the opportunistic human pathogen <italic>Pseudomonas aeruginosa</italic> (<italic>Pae</italic>), <italic>c</italic>arbon <italic>c</italic>atabolite <italic>r</italic>epression (CCR) orchestrates the hierarchical utilization of N and C sources, and impacts virulence, antibiotic resistance and biofilm development. During CCR, the RNA chaperone Hfq and the <italic>c</italic>atabolite <italic>r</italic>epression <italic>c</italic>ontrol protein Crc form assemblies on target mRNAs that impede translation of proteins involved in uptake and catabolism of less preferred C sources. After exhaustion of the preferred C-source, translational repression of target genes is relieved by the regulatory RNA CrcZ, which binds to and acts as a decoy for Hfq. Here, we asked whether Crc action can be modulated to relieve CCR after exhaustion of a preferred carbon source. As Crc does not bind to RNA <italic>per se</italic>, we endeavored to identify an interacting protein. <italic>In vivo</italic> co-purification studies, co-immunoprecipitation and biophysical assays revealed that Crc binds to <italic>Pae</italic> strain O1 protein PA1677. Our structural studies support bioinformatics analyzes showing that PA1677 belongs to the isochorismatase-like superfamily. Ectopic expression of PA<italic>1677</italic> resulted in de-repression of Hfq/Crc controlled target genes, while in the absence of the protein, an extended lag phase is observed during diauxic growth on a preferred and a non-preferred carbon source. This observations indicate that PA1677 acts as an antagonist of Crc that favors synthesis of proteins required to metabolize non-preferred carbon sources. We present a working model wherein PA1677 diminishes the formation of productive Hfq/Crc repressive complexes on target mRNAs by titrating Crc. Accordingly, we propose the name CrcA (<italic>c</italic>atabolite <italic>r</italic>epression <italic>c</italic>ontrol protein <italic>a</italic>ntagonist) for PA1677.</p>