Acute promyelocytic leukemia (APL) is characterized by reciprocal chromosomal translocations invariably involving the retinoic acid receptor alpha (RARalpha) gene on chromosome 17. In the vast majority of APL cases, the RARalpha gene is fused to the PML gene on chromosome 15, generating the fusion PML-RARalpha. The chimeric PML-RARalpha protein plays a critical role in APL leukemogenesis. Retinoic acid (RA) can overcome the differentiation block conferred by PML-RARalpha and induce APL cells to terminally maturate into granulocytes. However, resistance to RA develops both in vitro and in patients. We have developed RA-resistant subclones derived from the human APL cell line, NB4. These resistant subclones display altered RA-binding and reduced transactivation of retinoid response elements (RAREs) upon RA treatment. In the subclone R4, we identified a point mutation changing a leucine to praline in the ligand binding domain of the fusion PML-RARalpha protein that causes a loss of ligand binding. The mutant PML-RARalpha protein retains its ability to heterodimerize with RXRalpha and bind to RAREs. Thus, it functions as a dominant negative transcriptional inhibitor of the coexpressed wild-type RARalpha. The mutant PML-RARalpha has impaired RA-dependent interaction with receptor coregulatory factors, SMRT and ACTR. Histone deacetylase inhibitor, Trichostatin A (TSA), in combination with RA can overcome the dominant negative activity of the mutant PML-RARalpha in R4 and relieve transcriptional inhibition on RAREs. Further, TSA potentiates and partially restores RA-induced differentiation of NB4 and R4 cells respectively. When we examined the interaction of specific cofactors with retinoid receptors in NB4 cells compared to that in RA-resistant cell lines, we isolated the DRIP/TRAP protein complex. The ligand-inducible interaction between the DRIP/TRAP complex and retinoid receptors is independent of RA sensitivity and the expression of PML-RARalpha, supporting the glo
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36835 |
| Date | January 2000 |
| Creators | Shao, Wenlin, 1973- |
| Contributors | Miller, Wilson H., Jr. (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 (Division of Experimental Medicine.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001771015, proquestno: NQ69929, Theses scanned by UMI/ProQuest. |
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