title: Involvement of multiple DNA elements in iron-inducible transcription of the ap65-1 gene in the protozoan parasite Trichomonas vaginalis.
abstract: A reputed iron-responsive region, which contains multiple nuclear protein-binding DNA sequences, was shown previously to regulate iron-inducible transcription of the ap65-1 gene in the protozoan pathogen, Trichomonas vaginalis. These DNA sequences include two overlapping MYB recognition elements (MRE-1/MRE-2r) and three abutted T-tract elements. Additional nuclear protein-binding DNA sequences flanking the 5' (AGTGAAGTGA) and 3' (MRE-2f) of the iron-responsive region were identified in the present study. A stable promoter assay and primer extension revealed that transcriptional activity of the ap65-1 promoter is iron inducible as well as growth related, being lowest in the early logarithmic phase and highest in the mid-logarithmic phase. Subsequent mutational analysis of individual DNA elements of the ap65-1 promoter suggests that closely spaced T-tract elements together with an intervening GAAGGAAG sequence within the iron-responsive region are most critical for regulation of overall transcriptional activity, whereas an additional AGTGAAGTGA and MRE-2f together with an upstream T-rich region are required for optimal iron-inducible activity, and the MRE-1/MRE-2r overlap is only involved in growth-related activity. These observations suggest that expression of the ap65-1 gene is dynamically regulated under various growth conditions via interactions among multiple DNA regulatory elements.
authors.affiliation: Department of Parasitology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Shiou-Jeng
authors.initials: SJ
authors.lastname: Ong
authors.forename: Shen-Chi
authors.initials: SC
authors.lastname: Huang
authors.forename: Hsing-Wei
authors.initials: HW
authors.lastname: Liu
authors.forename: Jung-Hsiang
authors.initials: JH
authors.lastname: Tai
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015815:Cell Adhesion Molecules / Q000235:genetics*; D004252:DNA Mutational Analysis; D016054:DNA, Protozoan / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D007501:Iron / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015800:Protozoan Proteins / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic; D014246:Trichomonas vaginalis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: C096723:AP65-1 protein, Trichomonas vaginalis; D015815:Cell Adhesion Molecules; D016054:DNA, Protozoan; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D015800:Protozoan Proteins; D007501:Iron