title: Molecular basis of the recognition of the ap65-1 gene transcription promoter elements by a Myb protein from the protozoan parasite Trichomonas vaginalis.
abstract: Iron-inducible transcription of the ap65-1 gene in Trichomonas vaginalis involves at least three Myb-like transcriptional factors (tvMyb1, tvMyb2 and tvMyb3) that differentially bind to two closely spaced promoter sites, MRE-1/MRE-2r and MRE-2f. Here, we defined a fragment of tvMyb2 comprising residues 40-156 (tvMyb2₄₀₋₁₅₆) as the minimum structural unit that retains near full binding affinity with the promoter DNAs. Like c-Myb in vertebrates, the DNA-free tvMyb2₄₀₋₁₅₆ has a flexible and open conformation. Upon binding to the promoter DNA elements, tvMyb2₄₀₋₁₅₆ undergoes significant conformational re-arrangement and structure stabilization. Crystal structures of tvMyb2₄₀₋₁₅₆ in complex with promoter element-containing DNA oligomers showed that 5'-a/gACGAT-3' is the specific base sequence recognized by tvMyb2₄₀₋₁₅₆, which does not fully conform to that of the Myb binding site sequence. Furthermore, Lys⁴⁹, which is upstream of the R2 motif (amino acids 52-102) also participates in specific DNA sequence recognition. Intriguingly, tvMyb2₄₀₋₁₅₆ binds to the promoter elements in an orientation opposite to that proposed in the HADDOCK model of the tvMyb1₃₅₋₁₄₁/MRE-1-MRE-2r complex. These results shed new light on understanding the molecular mechanism of Myb-DNA recognition and provide a framework to study the molecular basis of transcriptional regulation of myriad Mybs in T. vaginalis.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, ROC.
authors.forename: Ingjye
authors.initials: I
authors.lastname: Jiang
authors.forename: Chen-Kun
authors.initials: CK
authors.lastname: Tsai
authors.forename: Sheng-Chia
authors.initials: SC
authors.lastname: Chen
authors.forename: Szu-Huan
authors.initials: SH
authors.lastname: Wang
authors.forename: Imamaddin
authors.initials: I
authors.lastname: Amiraslanov
authors.forename: Chi-Fon
authors.initials: CF
authors.lastname: Chang
authors.forename: Wen-Jin
authors.initials: WJ
authors.lastname: Wu
authors.forename: Jung-Hsiang
authors.initials: JH
authors.lastname: Tai
authors.forename: Yen-Chywan
authors.initials: YC
authors.lastname: Liaw
authors.forename: Tai-Huang
authors.initials: TH
authors.lastname: Huang
mesh_terms: D000595:Amino Acid Sequence; D015815:Cell Adhesion Molecules / Q000235:genetics*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D013816:Thermodynamics; D014246:Trichomonas vaginalis / Q000235:genetics
chemical_list: C096723:AP65-1 protein, Trichomonas vaginalis; D015815:Cell Adhesion Molecules; C520248:Myb2 protein, Trichomonas vaginalis; D015800:Protozoan Proteins; D004247:DNA