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Title: Regulation of Aggrecan gene expression by its promoter and Exon 1
Author: Palmer, Glyn Daniel
ISNI:       0000 0001 3465 6217
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1999
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Aggrecan is an essential component of articular cartilage and subject to regulation by tissue-specific and environmental factors. A series of studies were performed in order to identify regulatory elements in the human aggrecan gene, so that the molecular mechanisms that control its expression in chondrocytes can be further understood. A distal 1.7 kb portion of the aggrecan promoter was cloned and sequenced and found to contain an Alu repeat and several putative transcription factor binding motifs. In order to identify functionally important regions in the distal and proximal regions of the aggrecan promoter and 5’untranslated region (5’ UTR), a series of deletion constructs were created using luciferase reporter vectors in cell transfection assays. The results showed that the 5’UTR had a major effect on basal promoter activity, causing a 5- to 7-fold increase in luciferase expression in both chondrocytes and NIH 3T3 fibroblasts. Aggrecan promoter activity in chondrocytes was also found to be modulated by biochemical and physical stimuli including IL-1, TNFα, osmolality and shear stress. Results from deletion analysis showed that the 5’UTR is involved in conferring responsiveness to these factors, but other sequences in the 2.4 kb promoter are also involved. As well as extracellular factors, our studies demonstrated that aggrecan gene expression is modulated by a major intracellular signalling pathway. Blocking the activity of MEK-1 (MAPKK-1) in normal and transfected chondrocytes was found to induce a 4-fold increase in aggrecan mRNA levels and promoter activity. MEK-1 inhibition also prevented fluid-flow induced down-regulation of aggrecan promoter activity. Subsequent deletion analysis identified a 162 bp region in the 5’UTR that mediates responsiveness to MEK-1 signalling. The results obtained from this series of studies indicates that the 5’UTR contains at least two regions that regulate aggrecan gene expression; one region is essential for basal promoter activity, and the other modulates promoter activity in response to signals that stimulate the MEK-1/MAPK cascade.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Articular cartilage