Nuclear factor Y (NF-Y) mediated regulation of bone sialoprotein (bsp) gene transcription through an inverted CCAAT box.
Published: 2006
Language: eng
Number of pages: 147
ISBN-13: 9780494157862
Description: Bone sialoprotein (BSP) is a major extracellular matrix protein in bone and cementum that has been implicated in the nucleation of hydroxyapatite crystal formation during de novo osteogenesis. While generally restricted to mineralized tissues, BSP is also expressed by transformed cells that metastasize to bone. The proximal promoter region of the bsp  gene encompasses inverted CCAAT element (ICE) and TATA box that are highly conserved. To study the importance of the relative position and orientation of these regulatory elements in basal transcription mutated reporter constructs were analyzed in transient transfection assays. Whereas reverting the ICE-box reduced transcription markedly, reverting the flanking sequence with the ICE increased both transcription and NF-Y binding, progressively. Reducing the distance between the ICE and the TATA produced cyclical changes in transcription activity that correlated with the progressive alterations of the relative positions of the ICE and TATA on the face of the DNA helix. These studies showed that transcription efficiency is dependent on the relative orientation of the ICE and TATA elements and the flexibility of the DNA helix.Since basal transcription of bsp is stimulated by v-Src acting through the ICE-box the effects of c-Jun, which functions downstream of Src, were analyzed. c-Jun increased basal transcription in ROS 17/2.8 osteosarcoma cells through the recruitment of NF-Y, independently of DNA binding, phosphorylation by Jun-kinase, and HAT activities of p300/CBP and P/CAF. Unexpectedly the adenovirus gene, E1A, also stimulated bsp transcription through NF-Y, independently of c-Jun, and p300/CBP and P/CAF HAT activity. Although the proto(oncogenes) v-Src, c-Jun, and E1A increased bsp transcription in osteosarcoma cells and also non-bone transformed (HeLa and SW620) cells, little effect was evident in normal bone (RBMC-D8) and non-bone (MEF) cells, indicating that transcription in normal cells and stimulated expression in the transformed cells is dependent of NF-Y.Collectively the results of these studies, which are relevant to a broad range of genes that have an ICE-box, provide insights into the mechanism of basal transcription of the bsp gene in normal and transformed cells.
Notes: Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 2974.

Thesis (Ph.D.)--University of Toronto, 2006.

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