title: Eha, a transcriptional regulator of hemolytic activity of Edwardsiella tarda.
abstract: Hemolysis causes major symptoms such as the reddening skin and systemic hemorrhagic septicemia of diseased fish infected by Edwardsiella tarda. Cytolysin A (ClyA) is a pore-forming cytotoxic protein encoded by the clyA gene in Escherichia coli K-12. In this study, we observed that the heterologous expression of the eha gene from E. tarda could confer hemolytic activity upon a hemolytic-silent E. coli strain. The transcription of clyA is positively controlled by the eha gene in E. tarda by RT-PCR. We cloned and purified Eha protein which had shown preferential binding ability to the clyA sequences in its promoter region, as evidenced by gel shift assay. The eha controls the transcriptional start predominantly at 72 bp upstream in the clyA promoter region, as determined by primer extension assays. We suggest that Eha protein is a new positive regulator found in E. tarda. In addition, we constructed the eha mutant and complementary strains of E. tarda. The hemolytic activity of the eha mutant was found to be attenuated compared with the wild-type strain. The complementary strains restored the hemolytic activity to levels between those of the wild type and the eha mutation. Our results indicate that the Eha protein is an important positive regulator in the hemolytic properties of E. tarda.
authors.affiliation: Department of Pathogenic Microbiology and Immunology, Southeast University School of Medicine, Nanjing, China.
authors.forename: Daqing
authors.initials: D
authors.lastname: Gao
authors.forename: Jing
authors.initials: J
authors.lastname: Cheng
authors.forename: Enjin
authors.initials: E
authors.lastname: Zheng
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Li
authors.forename: Zeye
authors.initials: Z
authors.lastname: Shao
authors.forename: Zeyan
authors.initials: Z
authors.lastname: Xu
authors.forename: Chengping
authors.initials: C
authors.lastname: Lu
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D020609:Edwardsiella tarda / Q000235:genetics* / Q000502:physiology; D004756:Enterobacteriaceae Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005393:Fish Diseases / Q000382:microbiology*; D005399:Fishes; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006460:Hemolysin Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D006461:Hemolysis; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C119944:hlyE protein, E coli
keywords: Edwardsiella tarda; clyA gene; eha gene; hemolytic activity