title: Different degrees of structural order in distinct regions of the transcriptional repressor HES-1.
abstract: HES-1 is a transcriptional repressor of the basic helix-loop-helix (bHLH) family and one of the main downstream effectors in Notch signaling. Its domain architecture is composed of a bHLH region, an Orange domain, and a poorly characterized C-terminal half. We show that different degrees of structural order are present in the different regions of HES-1. The isolated bHLH domain is only marginally stable in solution, and partially folds upon dimerization. Binding to DNA promotes folding, stabilization, and protection from proteolysis of the bHLH domain. The Orange domain, on the contrary, is well folded in all conditions, forms stable dimers, and greatly increases protein resistance to thermal denaturation. The isolated proline-rich C-terminal region is mainly disordered in solution, and remains unstructured also in the full length protein. Measurements of binding constants show that HES-1 recognizes dsDNA synthetic oligonucleotides corresponding to several functional DNA targets with high affinity, but with relatively little specificity. We propose that order/disorder transitions in the different domains are associated not only with binding to DNA, but also with protein homo- and hetero-dimerization.
authors.affiliation: Protein Structure and Bioinformatics Group, International Center for Genetic Engineerintg and Biotechnology (ICGEB), AREA Science Park, Trieste, Italy.
authors.forename: Maristella
authors.initials: M
authors.lastname: Coglievina
authors.forename: Corrado
authors.initials: C
authors.lastname: Guarnaccia
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pintar
authors.forename: Sándor
authors.initials: S
authors.lastname: Pongor
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D000072056:Transcription Factor HES-1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004247:DNA; D018398:Homeodomain Proteins; D012097:Repressor Proteins; D000072056:Transcription Factor HES-1; C078493:HES1 protein, human