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csrR, a Paralog and Direct Target of CsrA, Promotes Legionella pneumophila Resilience in Water.

Abbott ZD, Yakhnin H, Babitzke P, Swanson MS - MBio (2015)

Bottom Line: A potent regulator of this pathogen's intracellular life cycle is CsrA, a protein widely distributed among bacterial species that is understood quite well.Our finding that every sequenced L. pneumophila strain carries several csrA paralogs-including two common to all isolates--indicates that the legionellae exploit CsrA regulatory switches for multiple purposes.Our discovery that one paralog, CsrR, is a target of CsrA that enhances survival in water is an important step toward understanding colonization of the engineered environment by pathogenic L. pneumophila.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.

No MeSH data available.


Related in: MedlinePlus

A putative CsrA binding site on the csrR RNA overlaps with a ribosome binding site motif. (A) The csrR transcriptional start site (TSS, +1; black arrow) was mapped by 5′ RACE. Likely −10 and −35 promoter elements are underlined and labeled; a putative Shine-Dalgarno (SD) sequence and the associated flanking bases predicted to form a stem-loop structure recognized by CsrA and located 10 bases 5′ of the translational start are underlined; and the csrR open reading frame is marked with a gray arrow and capitalized letters. (B) The csrR RNA encodes a putative SD (+37) sequence located on a stem-loop and an ATG start codon (+51) positioned at the base of two stem-loops, as predicted by the IDT UNAFold algorithm. CsrA protein is predicted to bind the csrR RNA SD sequence (boxed).
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fig3: A putative CsrA binding site on the csrR RNA overlaps with a ribosome binding site motif. (A) The csrR transcriptional start site (TSS, +1; black arrow) was mapped by 5′ RACE. Likely −10 and −35 promoter elements are underlined and labeled; a putative Shine-Dalgarno (SD) sequence and the associated flanking bases predicted to form a stem-loop structure recognized by CsrA and located 10 bases 5′ of the translational start are underlined; and the csrR open reading frame is marked with a gray arrow and capitalized letters. (B) The csrR RNA encodes a putative SD (+37) sequence located on a stem-loop and an ATG start codon (+51) positioned at the base of two stem-loops, as predicted by the IDT UNAFold algorithm. CsrA protein is predicted to bind the csrR RNA SD sequence (boxed).

Mentions: Because knowledge of a protein’s regulation can provide insight into its function, we next analyzed the upstream sequences of csrR. Bioinformatic analysis identified motifs typical of CsrA binding sites in the 5′ noncoding region of csrR (11). As a first step to analyze csrR regulation, we mapped by 5′ rapid amplification of cDNA ends (5′-RACE) its transcriptional start site to −52 relative to the translational start (data not shown). Three independent sequencing events revealed that the transcript starting with the −52 start site was predominant, although rare transcripts started at −53 or −54. On the basis of the data indicating the predominant species, we made several predictions about the csrR mRNA. Putative −10 and −35 sites as well as the likely SD sequence approximately 10 bases 5′ of the translational start codon were identified (Fig. 3A). RNA-fold software predicted a secondary structure for the csrR transcript in which the SD sequence is positioned in a loop extending from a long stem (Fig. 3B), a common binding motif for CsrA protein (38). Accordingly, we postulated that the csrR transcript is bound and its stability regulated by CsrA.


csrR, a Paralog and Direct Target of CsrA, Promotes Legionella pneumophila Resilience in Water.

Abbott ZD, Yakhnin H, Babitzke P, Swanson MS - MBio (2015)

A putative CsrA binding site on the csrR RNA overlaps with a ribosome binding site motif. (A) The csrR transcriptional start site (TSS, +1; black arrow) was mapped by 5′ RACE. Likely −10 and −35 promoter elements are underlined and labeled; a putative Shine-Dalgarno (SD) sequence and the associated flanking bases predicted to form a stem-loop structure recognized by CsrA and located 10 bases 5′ of the translational start are underlined; and the csrR open reading frame is marked with a gray arrow and capitalized letters. (B) The csrR RNA encodes a putative SD (+37) sequence located on a stem-loop and an ATG start codon (+51) positioned at the base of two stem-loops, as predicted by the IDT UNAFold algorithm. CsrA protein is predicted to bind the csrR RNA SD sequence (boxed).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4471563&req=5

fig3: A putative CsrA binding site on the csrR RNA overlaps with a ribosome binding site motif. (A) The csrR transcriptional start site (TSS, +1; black arrow) was mapped by 5′ RACE. Likely −10 and −35 promoter elements are underlined and labeled; a putative Shine-Dalgarno (SD) sequence and the associated flanking bases predicted to form a stem-loop structure recognized by CsrA and located 10 bases 5′ of the translational start are underlined; and the csrR open reading frame is marked with a gray arrow and capitalized letters. (B) The csrR RNA encodes a putative SD (+37) sequence located on a stem-loop and an ATG start codon (+51) positioned at the base of two stem-loops, as predicted by the IDT UNAFold algorithm. CsrA protein is predicted to bind the csrR RNA SD sequence (boxed).
Mentions: Because knowledge of a protein’s regulation can provide insight into its function, we next analyzed the upstream sequences of csrR. Bioinformatic analysis identified motifs typical of CsrA binding sites in the 5′ noncoding region of csrR (11). As a first step to analyze csrR regulation, we mapped by 5′ rapid amplification of cDNA ends (5′-RACE) its transcriptional start site to −52 relative to the translational start (data not shown). Three independent sequencing events revealed that the transcript starting with the −52 start site was predominant, although rare transcripts started at −53 or −54. On the basis of the data indicating the predominant species, we made several predictions about the csrR mRNA. Putative −10 and −35 sites as well as the likely SD sequence approximately 10 bases 5′ of the translational start codon were identified (Fig. 3A). RNA-fold software predicted a secondary structure for the csrR transcript in which the SD sequence is positioned in a loop extending from a long stem (Fig. 3B), a common binding motif for CsrA protein (38). Accordingly, we postulated that the csrR transcript is bound and its stability regulated by CsrA.

Bottom Line: A potent regulator of this pathogen's intracellular life cycle is CsrA, a protein widely distributed among bacterial species that is understood quite well.Our finding that every sequenced L. pneumophila strain carries several csrA paralogs-including two common to all isolates--indicates that the legionellae exploit CsrA regulatory switches for multiple purposes.Our discovery that one paralog, CsrR, is a target of CsrA that enhances survival in water is an important step toward understanding colonization of the engineered environment by pathogenic L. pneumophila.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.

No MeSH data available.


Related in: MedlinePlus