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IDENTIFICATION OF A NON-CLASSICAL GLUCOCORTICOID-RESPONSIVE ELEMENT IN THE 5'-FLANKING REGION OF THE CHICKEN GROWTH HORMONE GENE

dc.contributor.advisorPorter, Tom Een_US
dc.contributor.authorKnubel, Kristina Heucken_US
dc.date.accessioned2010-10-07T06:01:35Z
dc.date.available2010-10-07T06:01:35Z
dc.date.issued2010en_US
dc.identifier.urihttp://hdl.handle.net/1903/10902
dc.description.abstractGrowth hormone (GH) effects growth and contributes to a lean phenotype in broiler chickens. GH secretion by the anterior pituitary begins on embryonic day (e) 14, concomitantly with a rise in adrenal glucocorticoids (GC) or corticosterone (CORT) secretion. CORT treatment of chicken embryonic pituitary (CEP) cells induces GH secretion prematurely. GC induction of the GH gene requires on-going protein synthesis or an intermediary protein, but the gene lacks a classical GC-response element. We hypothesized that a GC-responsive intermediary protein is necessary for the CORT induced increase in GH. Characterization of the upstream region of the gene may help identify such a protein. To this end, a fragment of the GH gene (-1727/+48) was cloned into a luciferase reporter and characterized in e11 CEP cells. CORT treatment increased luciferase activity and mRNA. Inclusion of CHX blocked CORT induction of luciferase mRNA. Through deletion analysis, we found that a GC-responsive region (GCRR) is located at -1045 to -954. By defining the GC-responsive region and cis-acting elements located within, trans-acting proteins involved in GC induction of the GH gene may be identified. The GCRR is CORT-responsive in either orientation, but it is context-dependent. Potential transcription factor motifs in the GCRR include ETS-1 and a degenerate GRE (GREF). Nuclear proteins bound to a GCRR probe in a CORT-regulated manner and unlabeled competitor DNA competed off binding. Mutation of the central portion of the DNA probe resulted in a significant decrease in protein binding. Mutation of the ETS-1 site or GREF site in the -1045/+48 GH construct resulted in ablation of luciferase activity. ETS-1 and GR are associated with the endogenous gene under basal and 1.5 h CORT-treated conditions, while GR recruitment increased after CORT treatment. GC regulation of the GH gene during chicken embryonic development requires cis-acting elements located 1 kb upstream from the transcription start site and includes recruitment of ETS-1 and GR. This is the first study to demonstrate involvement of ETS-1 in GC regulation of the GH gene during embryonic development. Characterization of GC regulation of the GH gene during embryonic development enhances our understanding of growth regulation in vertebrates.en_US
dc.titleIDENTIFICATION OF A NON-CLASSICAL GLUCOCORTICOID-RESPONSIVE ELEMENT IN THE 5'-FLANKING REGION OF THE CHICKEN GROWTH HORMONE GENEen_US
dc.typeDissertationen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.contributor.departmentAnimal Sciencesen_US
dc.subject.pqcontrolledBiology, Molecularen_US
dc.subject.pqcontrolledBiology, Cellen_US
dc.subject.pqcontrolledBiology, Animal Physiologyen_US
dc.subject.pquncontrolledembryonic developmenten_US
dc.subject.pquncontrolledgeneen_US
dc.subject.pquncontrolledglucocorticoiden_US
dc.subject.pquncontrolledgrowth hormoneen_US
dc.subject.pquncontrolledluciferaseen_US
dc.subject.pquncontrolledreceptoren_US


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