title: bicaudal encodes the Drosophila beta NAC homolog, a component of the ribosomal translational machinery*.
abstract: bicaudal was the first Drosophila mutation identified as producing mirror-image pattern duplications along the anteroposterior axis of the embryo. However the mutation has been little studied due to its low penetrance and suppressibility. We undertook cloning of the bicaudal locus together with studies of the mutation's effects on key elements of the posterior embryonic patterning pathway. Our mapping studies place the bicaudal mutation within a approximately 2 kb region, 3' to the protein coding sequence of the Drosophila homolog of beta NAC, a subunit of Nascent polypeptide Associated Complex (NAC). Genomic DNA encoding beta NAC completely rescues the bicaudal phenotype. The lethal phenotype of Enhancer of Bicaudal, E(Bic), a mutation hypothesized to affect the bicaudal locus, is also completely rescued by the beta NAC locus. We further demonstrate that the E(Bic) mutation is caused by a P element insertion into the transcribed region of the beta NAC gene. NAC is among the first ribosome-associated entities to bind the nascent polypeptide after peptide bond formation. In contrast to other bicaudal-embryo-producing mutations, bicaudal leads to ectopic translation of mRNA for the posterior determinant nanos, without affecting the localization of mRNA for its upstream regulator, oskar, in the embryo. These findings suggest that repression of nanos mRNA translation occurs on the ribosome and involves a role for beta NAC.
authors.affiliation: Department of Biochemistry, Rice University, MS-140, Houston, TX 77005, USA. kate@bioc.rice.edu.
authors.forename: D C
authors.initials: DC
authors.lastname: Markesich
authors.forename: K M
authors.initials: KM
authors.lastname: Gajewski
authors.forename: M E
authors.initials: ME
authors.lastname: Nazimiec
authors.forename: K
authors.initials: K
authors.lastname: Beckingham
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics; D003001:Cloning, Molecular; D016384:Consensus Sequence; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009024:Morphogenesis; D014176:Protein Biosynthesis; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping; D012270:Ribosomes / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D018271:Signal Recognition Particle / Q000737:chemistry / Q000235:genetics; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics
chemical_list: C061998:BicD protein, Drosophila; D029721:Drosophila Proteins; D019476:Insect Proteins; D018832:Molecular Chaperones; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D018271:Signal Recognition Particle; C503637:Srp72 protein, mouse; D015534:Trans-Activators; C096099:nascent-polypeptide-associated complex; C091675:osk protein, Drosophila; C070574:nos protein, Drosophila