title: Clp upregulates transcription of engA gene encoding a virulence factor in Xanthomonas campestris by direct binding to the upstream tandem Clp sites.
abstract: In Xanthomonas campestris, the causative agent of black rot in crucifers, the endoglucanase level is greatly decreased in the mutant deficient in Clp, a homologue of cyclic AMP receptor protein (CRP). It is established that Clp has the same DNA binding specificity as CRP at positions 5, 6, and 7 (GTG motif) of the DNA half site. In this study, the engA transcription initiation site was determined by the 5' RACE method, and two consensus Clp-binding sites, site I and site II centered at -69.5 and -42.5, respectively, were located. Transcriptional fusion assays indicated that Clp greatly activates engA transcription. Site-directed mutagenesis indicated that position 5 of GTG motif in site II is essential for both DNA-protein complex formation in electrophoretic mobility shift assays and engA transcription in vivo. In addition, mutation at position 5 of site I drastically reduces the promoter activity, indicating that binding of Clp to site I exerts a synergistic effect on the transcription activation by site II. engA appears to be the first X. campestris gene known to be activated by Clp via a direct binding to the promoter.
authors.affiliation: Institute of Medical Biotechnology, Chungtai Institute of Health Sciences and Technology, Taichung 406, Taiwan, ROC.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Hsiao
authors.forename: Hsiu-Ying
authors.initials: HY
authors.lastname: Liao
authors.forename: Mong-Chuan
authors.initials: MC
authors.lastname: Lee
authors.forename: Tsuey-Ching
authors.initials: TC
authors.lastname: Yang
authors.forename: Yi-Hsiung
authors.initials: YH
authors.lastname: Tseng
mesh_terms: D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D024363:Transcription Initiation Site; D015533:Transcriptional Activation; D015854:Up-Regulation; D037521:Virulence Factors / Q000235:genetics*; D016959:Xanthomonas campestris / Q000235:genetics* / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; C436751:Clp protein, Xanthomonas campestris; D002373:Cyclic AMP Receptor Protein; D014157:Transcription Factors; D037521:Virulence Factors