title: Evolutionarily conserved domains required for activation and repression functions of the Drosophila Hox protein Ultrabithorax.
abstract: While testing the functions of deletion mutants in the Hox protein Ultrabithorax (Ubx), we found that the embryonic repression function of Ubx on Distal-less transcription in limb primordia is highly concentration dependent. The steep sigmoidal relationship between in vivo Ubx concentration and Distal-less repression is dependent on the Ubx YPWM motif. This suggests that Ubx cooperatively assembles a multi-protein repression complex on Distal-less regulatory DNA with the YPWM motif as a key protein-protein interface in this complex. Our deletion mutants also provide evidence for a transcriptional activation domain in the N-terminal 19 amino acids of Ubx. This proposed activation domain contains a variant of the SSYF motif that is found at the N termini of many Hox proteins, and is conserved in the activation domain of another Hox protein, Sex combs reduced. These results suggest that the N-terminal region containing the SSYF motif has been conserved in many Hox proteins for its role in transcriptional activation.
authors.affiliation: Section in Cell and Developmental Biology, Division of Biology, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Ella
authors.initials: E
authors.lastname: Tour
authors.forename: Chris Todd
authors.initials: CT
authors.lastname: Hittinger
authors.forename: William
authors.initials: W
authors.lastname: McGinnis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017124:Conserved Sequence / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D046912:Multiprotein Complexes; D009154:Mutation; D012097:Repressor Proteins; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D046912:Multiprotein Complexes; D012097:Repressor Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila