title: LexA-independent DNA damage-mediated induction of gene expression in Myxococcus xanthus.
abstract: Myxococcus xanthus, a member of the Proteobacteria delta-class, has two independent recA genes, recA1 and recA2, but only recA2 is DNA damage-inducible. The lexA gene has been isolated from M. xanthus by PCR amplification with oligonucleotides designed after sequence identification by tblastn analysis of its genome at the Cereon Microbial Sequence Database. The M. xanthus purified LexA protein is shown to bind specifically to the consensus sequence CTRHAMRYBYGTTCAGS present upstream of lexA and recA2. A degenerate copy of this motif but with important differences can be identified in the region upstream of the recA1 gene. A knock-out lexA(Def) mutant that has been generated does not differ significantly from wild type in morphology, growth rate, light-induced carotenogenesis or development. Using transcriptional lacZ fusions and quantitative RT-PCR analysis, it has been demonstrated that expression of both lexA and recA2 genes is constitutive in the lexA(Def) mutant, whereas the transcription of the DNA damage non-inducible recA1 gene is not affected in this strain. recN and ssb, whose expression in Escherichia coli are LexA-regulated, are induced by DNA damage in the M. xanthus lexA(Def) mutant. These data reveal the existence of different regulatory mechanisms for DNA damage-inducible genes in bacteria belonging to different phyla.
authors.affiliation: Departament de Genética i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Campoy
authors.forename: Marta
authors.initials: M
authors.lastname: Fontes
authors.forename: S
authors.initials: S
authors.lastname: Padmanabhan
authors.forename: Pilar
authors.initials: P
authors.lastname: Cortés
authors.forename: Montserrat
authors.initials: M
authors.lastname: Llagostera
authors.forename: Jordi
authors.initials: J
authors.lastname: Barbé
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004249:DNA Damage; D004269:DNA, Bacterial / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016941:Myxococcus xanthus / Q000187:drug effects / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D013014:SOS Response, Genetics; D012697:Serine Endopeptidases / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein