title: ProQ/FinO-domain proteins: another ubiquitous family of RNA matchmakers?
abstract: Small RNAs (sRNAs), particularly those that act by limited base pairing with mRNAs, are part of most regulatory networks in bacteria. In many cases, the base-pairing interaction is facilitated by the RNA chaperone Hfq. However, not all bacteria encode Hfq and some base-pairing sRNAs do not require Hfq raising the possibility of other RNA chaperones. Candidates are proteins with homology to FinO, a factor that promotes base pairing between the FinP antisense sRNA and the traJ mRNA to control F plasmid transfer. Recent papers have shown that the Salmonella enterica FinO-domain protein ProQ binds a large suite of sRNAs, including the RaiZ sRNA, which represses translation of the hupA mRNA, and the Legionella pneumophila protein RocC binds the RocR sRNA, which blocks expression of competence genes. Here we discuss what is known about FinO-domain structures, including the recently solved Escherichia coli ProQ structure, as well as the RNA binding properties of this family of proteins and evidence they act as chaperones. We compare these properties with those of Hfq. We further summarize what is known about the physiological roles of FinO-domain proteins and enumerate outstanding questions whose answers will establish whether they constitute a second major class of RNA chaperones.
authors.affiliation: Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, Poznan, 61-614, Poland.
authors.forename: Mikolaj
authors.initials: M
authors.lastname: Olejniczak
authors.affiliation: Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institutes of Child Health and Human Development, Bethesda, MD, 20892-4417, USA.
authors.forename: Gisela
authors.identifier: http://orcid.org/0000-0001-6698-1241
authors.initials: G
authors.lastname: Storz
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism* / Q000502:physiology*; D005144:F Factor; D018832:Molecular Chaperones / Q000378:metabolism; D009690:Nucleic Acid Conformation; D000072417:Protein Domains; D016372:RNA, Antisense / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D012097:Repressor Proteins / Q000378:metabolism* / Q000502:physiology; D013329:Structure-Activity Relationship
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; C118132:ProQ protein, E coli; D016372:RNA, Antisense; D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C074275:FinO protein, E coli