title: Impaired synthesis and secretion of SopA in Salmonella Typhimurium dam mutants.
abstract: DNA adenine methylation regulates virulence gene expression in certain bacteria, including Salmonella Typhimurium. The aim of this study was to investigate the involvement of DNA adenine methylase (Dam) methylation in the expression and secretion of the SPI-1 effector protein SopA. For this purpose, SopA-FLAG-tagged wild-type and dam strains of Salmonella Typhimurium were constructed. The expression and secretion of SopA were determined in bacterial culture and in intracellular bacteria recovered from infected HEp-2 epithelial cells. Bacterial culture supernatants and pellets were used to investigate secreted proteins and cell-associated proteins, respectively. Western blot and quantitative reverse transcriptase PCR analysis showed that the dam mutant expresses lower levels of SopA than the wild-type strain. Interestingly, the strain lacking Dam synthesizes SopA under nonpermissive conditions (28 degrees C). In addition, SopA secretion was drastically impaired in the dam mutant. In vivo experiments showed that the intracellular Salmonella dam mutant synthesizes SopA although in lower amounts than the wild-type strain. Taken together, our results suggest that Dam methylation modulates the expression and secretion of SopA in Salmonella Typhimurium.
authors.affiliation: CEFYBO-CONICET, Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina. monicagiaco@gmail.com
authors.forename: Mónica N
authors.initials: MN
authors.lastname: Giacomodonato
authors.forename: Sebastián H
authors.initials: SH
authors.lastname: Sarnacki
authors.forename: Mariángeles Noto
authors.initials: MN
authors.lastname: Llana
authors.forename: Alejandra S
authors.initials: AS
authors.lastname: García Cattaneo
authors.forename: Sergio
authors.initials: S
authors.lastname: Uzzau
authors.forename: Salvatore
authors.initials: S
authors.lastname: Rubino
authors.forename: María Cristina
authors.initials: MC
authors.lastname: Cerquetti
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D015153:Blotting, Western; D002460:Cell Line; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000235:genetics* / Q000378:metabolism; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C060971:SopA protein, Bacteria