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Different olfactory cues elicit distinct behaviors such as attraction, avoidance, feeding, or mating. In the nematode C. elegans, these cues are sensed by a small number of olfactory neurons, each of which expresses several different odorant receptors. The type of behavioral response elicited by an odorant could be specified by the olfactory receptor or by the olfactory neuron in which the receptor...
We have reconstituted the ubiquitination pathway for the Cdk inhibitor Sic1 using recombinant proteins. Skp1, Cdc53, and the F-box protein Cdc4 form a complex, SCF Cdc4 , which functions as a Sic1 ubiquitin-ligase (E3) in combination with the ubiquitin conjugating enzyme (E2) Cdc34 and E1. Cdc4 assembled with Skp1 functions as the receptor that selectively binds phosphorylated...
We show that homothorax (hth) is required for the Hox genes to pattern the body of the fruit fly, Drosophila melanogaster. hth is necessary for the nuclear localization of an essential HOX cofactor, Extradenticle (EXD), and encodes a homeodomain protein that shares extensive identity with the product of Meis1, a murine proto-oncogene. MEIS1 is able to rescue hth mutant phenotypes and can induce the...
NEM prevents mitotic reassembly of Golgi cisternae into stacked structures. The major target of NEM is a 65 kDa protein conserved from yeast to mammals. Antibodies to this protein and a recombinant form of it block cisternal stacking in a cell-free system, justifying its designation as a Golgi ReAssembly Stacking Protein (GRASP65). One of the two minor targets of NEM is GM130, previously implicated...
The structural organization of encapsidated T7 DNA was investigated by cryo-electron microscopy and image processing. A tail-deletion mutant was found to present two preferred views of phage heads: views along the axis through the capsid vertex where the connector protein resides and via which DNA is packaged; and side views perpendicular to this axis. The resulting images reveal striking patterns...
The crystal structure of the substrate binding domain of the thermosome, the archaeal group II chaperonin, has been determined at 2.3 Å resolution. The core resembles the apical domain of GroEL but lacks the hydrophobic residues implied in binding of substrates to group I chaperonins. Rather, a large hydrophobic surface patch is found in a novel helix-turn-helix motif, which is characteristic of all...
Recently we purified a 900 kDa cytokine-responsive IκB kinase complex (IKK) and molecularly cloned one of its subunits, IKKα, a serine kinase. We now describe the molecular cloning and characterization of IKKβ, a second subunit of the IKK complex. IKKβ is 50% identical to IKKα and like it contains a kinase domain, a leucine zipper, and a helix-loop-helix. Although IKKα and IKKβ can undergo homotypic...
Growth factors can promote cell survival by activating the phosphatidylinositide-3'-OH kinase and its downstream target, the serine-threonine kinase Akt. However, the mechanism by which Akt functions to promote survival is not understood. We show that growth factor activation of the Pl3'K/Akt signaling pathway culminates in the phosphorylation of the BCL-2 family member BAD, thereby suppressing apoptosis...
In S. cerevisiae, the G1/S transition requires Cdc4p, Cdc34p, Cdc53p, Skp1p, and the Cln/Cdc28p cyclindependent kinase (Cdk). These proteins are thought to promote the proteolytic inactivation of the S-phase Cdk inhibitor Sic1p. We show here that Cdc4p, Cdc53p, and Skp1p assemble into a ubiquitin ligase complex named SCF Cdc4p . When mixed together, SCF Cd ...
Cyclooxygenase (COX) is the rate-limiting enzyme in the synthesis of prostaglandins (PGs) and exists in two isoforms, COX-1 and COX-2. In spite of long-standing speculation, definitive roles of PGs in various events of early pregnancy remain elusive. We demonstrate herein that the targeted disruption of COX-2, but not COX-1, in mice produces multiple failures in female reproductive processes that...
The homeobox gene GBX2 was identified as a target gene of the v-Myb oncoprotein encoded by the avian myeloblastosis virus (AMV). GBX2 activation by c-Myb requires signal transduction emanating from the cell surface while the leukemogenic AMV v-Myb constitutively induces the GBX2 gene. Mutations in the DNA binding domain of AMV-Myb render it independent of signaling events and concomitantly abrogate...
Molecular mechanisms determining methylation patterns in eukaryotic genomes still remain unresolved. We have characterized, in Ascobolus, a gene for de novo methylation. This novel eukaryotic gene, masc1, encodes a protein that has all motifs of the catalytic domain of eukaryotic C5- DNA-methyltransferases but is unique in that it lacks a regulatory N-terminal domain. The disruption of masc1 has no...
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