The pro-opiomelanocortin gene encodes protein precursor expressed primarily by the anterior pituitary corticotrophs and intermediate lobe melanotrophs. Pituitary expression of the POMC gene provides a paradigm for studying both tissue-specific and hormonally-regulated gene expression. The POMC promoter is composed of at least 13 different regulatory elements binding many different classes of transcription factors. There are several E-box sequences present in the POMC promoter, including elements DE-2C, CE-1A, and CE-1B. E-box elements bind members of the helix-loop-helix family of transcription factors. These factors exhibit either ubiquitous or cell-restricted expression patterns. The DE-2C element binds cell-specific HLH factors termed CUTE (Corticotroph Upstream Transcription Element) binding factors. / This study examines the role of the ubiquitous HLH transcription factors on POMC expression. Northern blot analysis revealed that all of the ubiquitous HLH factors, Pan 1, Pan 2, HEB, and ITF-2 are expressed in POMC-expressing AtT-20 cells, as is the neurally-restricted factor Mash-1. Overexpression of these factors revealed that the ubiquitous factors act on the CE-1B E-box, but not the DE-2C nor CE-1A elements. This finding was confirmed with gel retardation analysis; CE-1B binds overexpressed ITF-2, whereas DE-2C does not. Finally, the activity of the DE-2C element cannot be reconstituted in a non-POMC expressing cell line with the ubiquitous HLH factors alone. Collectively these experiments define a new transcriptional element contributing to POMC gene expression, CE-1B. The ubiquitously expressed members of the HLH family activate POMC transcription through this element; however, these factors alone cannot account for the activity of the CUTE factors.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.23412 |
| Date | January 1995 |
| Creators | McDonald, Scott, 1970- |
| Contributors | Drovin, J. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Division of Experimental Medicine.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001481333, proquestno: MM12241, Theses scanned by UMI/ProQuest. |
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