Ornithine Aminotransferase (OAT) is expressed at high levels in liver, kidney, and retina. Tissue-specific regulation of OAT has been described for rat kidney and liver. To characterize OAT regulation in retinal lines, we studied OAT synthesis in retinoblastomas RB355 and Y79. / OAT transcription and mRNA levels in the two lines were similar, but 3-fold greater immunoreactive OAT protein and enzyme activity were observed for Y79. Characterization of polysome-associated OAT mRNAs indicated that they were translated less efficiently, due to decreased initiation, in RB355. Initiation factor eIF-4E mRNA and protein were reduced in RB355; eIF-4E overexpression in RB355 increased OAT translation and OAT protein to the level observed in Y79. / Estrogen and thyroid hormone increased OAT expression in both strains. Estrogen increased translational initiation, with no effect on transcription, whereas thyroid hormone was primarily a transcriptional activator. / An alternatively-spliced OAT mRNA was identified in these retinoblastomas; this mRNA was poorly translated and was not affected by eIF-4E overexpression, estrogen, or thyroid hormone. / This study has demonstrated several post-transcriptional regulatory mechanisms for OAT in retinal tissue.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.70324 |
| Date | January 1991 |
| Creators | Fagan, Richard Joseph |
| Contributors | Rozen, Rima (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 | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001274913, proquestno: AAINN74800, Theses scanned by UMI/ProQuest. |
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