Comparative Genomics and Evolutionary Analysis of RNA-Binding Proteins of the CsrA Family in the Genus Pseudomonas

PATRICIO SOBRERO; CLAUDIO VALVERDE

Frontiers in Molecular Biosciences

Frontiers

Lugar: Lausanne; Año: 2020

Gene expression is adjusted according to cellular needs through a combination ofmechanisms acting at different layers of the flow of genetic information. At theposttranscriptional level, RNA-binding proteins are key factors controlling the fate ofnascent and mature mRNAs. Among them, the members of the CsrA family are smalldimeric proteins with heterogeneous distribution across the bacterial tree of life, thatact as global regulators of gene expression because they recognize characteristicsequence/structural motifs (short hairpins with GGA triplets in the loop) present inhundreds of mRNAs. The regulatory output of CsrA binding to mRNAs is counteractedin most cases by molecular mimic, non-protein coding RNAs that titrate the CsrAdimers away from the target mRNAs. In g-proteobacteria, the regulatory modulescomposed by CsrA homologs and the corresponding antagonistic sRNAs, are masteredby two-component systems of the GacS-GacA type, which control the transcription andthe abundance of the sRNAs, thus constituting the rather linear cascade Gac-Rsm thatresponds to environmental or cellular signals to adjust and coordinate the expressionof a set of target genes posttranscriptionally. Within the g-proteobacteria, the genusPseudomonas has been shown to contain species with different number of activeCsrA homologs and of molecular mimic sRNAs. Here, with the help of the increasingavailability of genomic data we provide a comprehensive state-of-the-art picture of theremarkable multiplicity of CsrA lineages, including novel yet uncharacterized paralogues,and discuss evolutionary aspects of the CsrA subfamilies of the genus Pseudomonas,and implications of the striking presence of csrA alleles in naturalmobile genetic elements(phages and plasmids).