SUMMARY The mechanisms by which clock neurons in the Drosophila brain confer an ~24-hr rhythm onto locomotor activity are unclear, but involve the neuropeptide diuretic hormone 44 (DH44), an ortholog of corticotropin-releasing factor. Here we identified DH44 receptor 1 as the relevant receptor for rest:activity rhythms and mapped its site of action to hugin-expressing neurons in the subesophageal zone (SEZ). We traced a circuit that extends from Dh44-expressing neurons in the pars intercerebralis (PI) through hugin+ SEZ neurons to the ventral nerve cord. Hugin neuropeptide, a neuromedin U ortholog, also regulates behavioral rhythms. The DH44 PI-Hugin SEZ circuit controls circadian locomotor activity in a daily cycle but has minimal effect on feeding rhythms, suggesting that the circadian drive to feed can be separated from circadian locomotion. These findings define a linear peptidergic circuit that links the clock to motor outputs to modulate circadian control of locomotor activity.

The ES oncoprotein of bovine papillomavirus, only 44 amino adds long, occurs as a disulfide-bonded transmembrane dimer. This remarkable oncoprotein stimulates signal transduction.through activation of the plateletderived growth factor (PDGF) receptor, and E5 exhibits limited amino acid sequence similarit with PDGF. Results presented here sugest that a key feature of the hydrophobic transmembrane domain is an amino acid side chain that participates in interhelical hydrogen bond formation. These data are reminiscent of the activated neu oncogene, in which a point mutation in the membrane domain leads to lipndindependent dimerization and activation of a receptor tyrosine kinase. Signfcantly, the tranmembrane domain of E5 can be largely replaced by the transmembrane domain from the activated neu receptor tyrosine kinase. Extensive mutageneis defines the minimal structural features required for transformation by the ES oncoprotein as, first, the ability to dimerize and, second, presentation ofa negatively charged residue at the extralular side of the membrane. The biological activity of ES mutants that lack most amino acid residues similar to PDGF snggests that ES and PDGF activate the PDGF receptor by disnct mechanisms.Bovine papillomavirus type I (BPV) typifies the fibropapilloma viruses, which transform fibroblasts in vitro and lead to development of fibrosarcomas in their host. In contrast, the human papillomaviruses infect epithelial cells and are strongly implicated in carcinomas of the cervix and respiratory tract (1). The fibroblast-transforming function of BPV is due to a small open reading frame, designated E5, encoding a 44-residue protein that forms membrane-associated disulfide-bonded dimers (2-6). Recent work has demonstrated that the E5 oncoprotein activates the platelet-derived growth factor (PDGF) P-receptor (7,8) and may display functional similarity with the human T-lymphotropic virus type I p12' protein (9).Inspection of the amino acid sequence of the E5 oncoprotein reveals two distinct domains (2-6): an extremely hydrophobic N-terminal domain, residues 1-32, and a hydrophilic C-terminal domain, residues 33-44. Several studies have led to the conclusion that the E5 oncoprotein is membraneanchored with a type II orientation, with the N terminus intracellular and the C terminus extracellular (10). In addition, the hydrophobic domain of E5 can function as a signal-anchor domain, indistinguishable from signal-anchor domains of well-characterized type II proteins such as neuraminidase, transferrin receptor, or asialoglycoprotein receptor (11).In this work, we describe the minimal structural features required for biological transforming activity by a transmembrane peptide. The results presented here suggest that E5 and PDGF activate the PDGF receptor by fundamentally distinct mechanisms. ES/neu Substitution Mutant. Degenerate oligonucleotides were synthesized that would encode a pool of E5/neu transmembrane recombinants in which the 44 residues would be derived as follows: 1-5 from E5, 6-10 from...