SHP-1, a SH2 domain-containing protein-tyrosine phosphatase, plays a critical role in regulation of cell signal transduction. SHP-1 is expressed not only in cells of hematopoietic lineages, but also in many non-hematopoietic cells under the control of a tissue-specific promoter, P1. In the first part of this thesis, the activity of the P1 promoter was analyzed in a region spanning 3.5 kb upstream of the major transcription start site in non-hematopoietic MCF-7 cells. An upstream Sp1 element (-126 to -118) positively regulated this TATA-box-lacking promoter. Two inverted CCAAT-elements (-332 to -328 and -66 to -62) played the important, but opposite roles, and transcription factor NF-Y predominantly bound to the two CCAAT-elements to control SHP-1 gene expression. Furthermore, incubation of MCF7 cells with 100 ng/ml trichostatin A (TSA), an inhibitor of histone deacetylase, significantly increased the activity of the P1 promoter. Mutation in the proximal CCAAT-element, however, eliminated the activating effect of trichostatin A on the promoter. In the second part of this thesis, the mechanism by which SHP-1 modulated TSA-induced MCF-7 cell apoptosis was elucidated. Analysis of cell survival signaling pathways revealed that overexpression of SHP-1 inactivated Akt ( eg. diminished phosphorylation resulted from modulation of PI3K expression) and increased caspase-9 and caspase-7 activities. Interestingly, a parallel decrease was observed in the phosphorylation of the pro-apoptosic Bcl-2 family member Bad at Ser112 as well as in the stress-activated MAP kinase JNK, both of which have been implicated in Akt- as well as ERK1/2-mediated functions. It was not surprising, therefore, to detect a diminished level of phosphorylated ERK1/2 in SHP-1-overexpressiog cells and that this effect was exacerbated by TSA treatment. Taken together, the data presented in this thesis suggest that SHP-1 expression is regulated by Sp1 and NF-Y factors, and SHP-1 sensitizes MCF-7 cells to TS
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.38441 |
| Date | January 2001 |
| Creators | Xu, Yan, 1958- |
| Contributors | Zhao, Xin (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 Animal Science.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001872076, proquestno: NQ78802, Theses scanned by UMI/ProQuest. |
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