title: Characterization of Xanthomonas axonopodis pv. citri LexA: recognition of the LexA binding site.
abstract: Levels of l exA transcripts are markedly increased upon exposure of Xanthomonas axonopodis pathovar citri ( X. a. pv. citri) to the DNA-damaging agent mitomycin C. Preliminary electrophoretic mobility-shift data led us to propose that binding of LexA protein to the sequence upstream of the lexA coding region is responsible for low promoter activity in the uniduced state. We determined that the LexA protein binds to the region located between the transcription start site and the translation initiation codon of the lexA gene of X. a. pv. citri. Using a DNase I footprinting technique, we identified a 19-bp palindromic sequence, TTAGTAGTAATACTACTAA (TTAGN(11)CTAA), located in this region as the binding sequence for the LexA protein of X. a. pv. citri, and showed that the two halves of the palindrome have to be in the inverted repeat orientation to permit binding of LexA. We also showed that almost any mutation in this sequence, including changes in the length of the spacer region of the palindrome, destroyed its ability to bind LexA both in vitro and in vivo.
authors.affiliation: Department of Life Science, Fu Jen University, 510 Chun-Chen Road, Taipei 242, Taiwan, Republic of China. mkyang@mails.fju.edu.tw
authors.forename: M-K
authors.initials: MK
authors.lastname: Yang
authors.forename: Y-C
authors.initials: YC
authors.lastname: Yang
authors.forename: C-H
authors.initials: CH
authors.lastname: Hsu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018983:DNA Footprinting; D017931:DNA Primers / Q000737:chemistry; D004269:DNA, Bacterial / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D016685:Mitomycin / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D013014:SOS Response, Genetics / Q000235:genetics*; D017384:Sequence Deletion; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D014974:Xanthomonas / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D003850:Deoxyribonuclease I; D016685:Mitomycin; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein