Pakistan Research Repository

AML AS TRANSCRIPTIONAL REGULATOR AND OSTEOBLAST DIFFERENTIATION MEDIATOR

Javed, Amjad (2000) AML AS TRANSCRIPTIONAL REGULATOR AND OSTEOBLAST DIFFERENTIATION MEDIATOR. PhD thesis, University of the Punjab, Lahore.

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Abstract

Three AML motifs are strategically positioned in the bone-specific rat osteocalcin (OC) promoter. Sites A and B flank the vitamin D response element (VDRE) in the distal promoter and sites Band C define the borders of a positioned nucleosome in the proximal promoter. The functional significance of each AML element was addressed by mutating individual or multiple AML sites within the context of the native rat (-1.1 kb) OC promoter-CAT. Reporter gene activity was assayed following transient transfection and after stable genomic integration in ROS 17/2.8 osteoblastic cell lines. It has been shown that all three AML sites are required for maximal basal expression of the rOC promoter. Furthermore, the distal sites A and B can functionally compensate for a mutation at the proximal site C and paired mutations involving site A (mAB or mAC) result in a loss of activity nearly equivalent to mutation of all three sites (mABC). Strikingly, mutation of the three AML sites leads to abrogation of responsiveness to vitamin D, glucocorticoids and TGF-B. We also find mutation of the three AML sites results in loss of the DNase hypersensitive sites at the VDRE and over the proximal tissue-specific basal promoter. These findings strongly support a multifunctional role for AML factors in regulating gene expression, not only as a simple transactivator, but also by facilitating modification in promoter architecture and chromatin organization.

Item Type:Thesis (PhD)
Uncontrolled Keywords:AML, rat osteocalcin, vitamin D response element (VDRE), Osteoblast, Bone resorption, DNA
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Paleo-zoology(c1.10)
ID Code:355
Deposited By:Mr Ghulam Murtaza
Deposited On:30 Jun 2006
Last Modified:04 Oct 2007 21:00

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