title: Biochemical and genetic studies of UBR3, a ubiquitin ligase with a function in olfactory and other sensory systems.
abstract: Our previous work identified E3 ubiquitin ligases, termed UBR1-UBR7, that contain the approximately 70-residue UBR box, a motif important for the targeting of N-end rule substrates. In this pathway, specific N-terminal residues of substrates are recognized as degradation signals by UBR box-containing E3s that include UBR1, UBR2, UBR4, and UBR5. The other E3s of this set, UBR3, UBR6, and UBR7, remained uncharacterized. Here we describe the cloning and analyses of mouse UBR3. The similarities of UBR3 to the UBR1 and UBR2 E3s of the N-end rule pathway include the RING and UBR domains. We show that HR6A and HR6B, the E2 enzymes that bind to UBR1 and UBR2, also interact with UBR3. However, in contrast to UBR1 and UBR2, UBR3 does not recognize N-end rule substrates. We also constructed UBR3-lacking mouse strains. In the 129SvImJ background, UBR3-/- mice died during embryogenesis, whereas the C57BL/6 background UBR3-/- mice exhibited neonatal lethality and suckling impairment that could be partially rescued by litter size reduction. The adult UBR3-/- mice had female-specific behavioral anosmia. Cells of the olfactory pathway were found to express beta-galactosidase (LacZ) that marked the deletion/disruption UBR3- allele. The UBR3-specific LacZ expression was also prominent in cells of the touch, vision, hearing, and taste systems, suggesting a regulatory role of UBR3 in sensory pathways, including olfaction. By analogy with functions of the UBR domain in the N-end rule pathway, we propose that the UBR box of UBR3 may recognize small compounds that modulate the targeting, by this E3, of its currently unknown substrates.
authors.affiliation: Center for Pharmacogenetics and Department of Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Tasaki
authors.affiliation: Institute of Pharmacology and Toxicology, Charité-University Medicine Berlin, Campus Mitte, Dorotheenstrasse 94, D-10117 Berlin, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Sohr
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena, California 91125.
authors.forename: Zanxian
authors.initials: Z
authors.lastname: Xia
authors.affiliation: Department of Psychiatry and Psychotherapy, Charité-University Medicine Berlin, Campus Benjamin Franklin, Eschenallee 3, D-14050 Berlin, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hellweg
authors.affiliation: Institute of Pharmacology and Toxicology, Charité-University Medicine Berlin, Campus Mitte, Dorotheenstrasse 94, D-10117 Berlin, Germany.
authors.forename: Heide
authors.initials: H
authors.lastname: Hörtnagl
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena, California 91125.
authors.forename: Alexander
authors.initials: A
authors.lastname: Varshavsky
authors.affiliation: Center for Pharmacogenetics and Department of Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15261. Electronic address: yok5@pitt.edu.
authors.forename: Yong Tae
authors.initials: YT
authors.lastname: Kwon
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D005982:Glutathione Transferase / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008954:Models, Biological; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012903:Smell; D014018:Tissue Distribution; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: C522185:UBR3 protein, mouse; D044767:Ubiquitin-Protein Ligases; D005982:Glutathione Transferase; D001616:beta-Galactosidase