title: Distinct HOX N-terminal arm residues are responsible for specificity of DNA recognition by HOX monomers and HOX.PBX heterodimers.
abstract: Dimerization with extradenticle or PBX homeoproteins dramatically improves DNA binding by HOX transcription factors, indicating that recognition by such complexes is important for HOX specificity. For HOX monomeric binding, a major determinant of specificity is the flexible N-terminal arm. It makes base-specific contacts via the minor groove, including one to the 1st position of a 5'-TNAT-3' core by a conserved arginine (Arg-5). Here we show that Arg-5 also contributes to the stability of HOX.PBX complexes, apparently by forming the same DNA contact. We further show that heterodimers of PBX with HOXA1 or HOXD4 proteins have different specificities at another position recognized by the N-terminal arm (the 2nd position in the TNAT core). Importantly, N-terminal arm residues 2 and 3, which distinguish the binding of HOXA1 and HOXD4 monomers, play no role in the specificity of their complexes with PBX. In addition, HOXD9 and HOXD10, which are capable of binding both TTAT and TAAT sites as monomers, can cooperate with PBX1A only on a TTAT site. These data suggest that some DNA contacts made by the N-terminal arm are altered by interaction with PBX.
authors.affiliation: McGill Cancer Centre, McGill University, Montréal, Québec H3G 1Y6, Canada.
authors.forename: M L
authors.initials: ML
authors.lastname: Phelan
authors.forename: M S
authors.initials: MS
authors.lastname: Featherstone
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D029721:Drosophila Proteins; D018398:Homeodomain Proteins / Q000737:chemistry / Q000378:metabolism*; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry / Q000378:metabolism*; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D016385:TATA Box; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D029961:Zebrafish Proteins; D000099261:Homeobox A1 Protein
chemical_list: D004247:DNA; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; D000099261:Homeobox A1 Protein; C062393:Abd-B proteins, Drosophila; C099223:hoxd10a protein, zebrafish; C083400:PBX1 protein, human