Modulation of DNA topoisomerase II alpha promoter activity by members of the Sp (specificity protein) and NF-Y (nuclear factor Y) families of transcription factors.

Abstract

Topo IIalpha (topoisomerase IIalpha) is a major target of several commonly used anticancer drugs and is subject to down-regulation at the transcriptional level in some drug-resistant cell lines and tumours in response to chemotherapy. Clinical resistance to such drugs has been correlated with down-regulation of topo IIalpha at transcription in some drug-resistant cell lines and tumours. Putative binding sites for a variety of transcription factors, including Sp1 (specificity protein 1) and NF-Y (nuclear factor Y) have previously been identified in the topo IIalpha promoter, but their functional significance and interactions have not been described following exposure to anti-cancer drugs. The binding of these factors to specific putative regulatory elements in the topo IIalpha promoter was studied using electrophoretic-mobility-shift assays. Sp1 was found to bind strongly to both distal and proximal GC-rich elements and NF-Y to ICB1 (the first inverted CCAAT box). The functional significance of transcription-factor binding was studied using transient transfection of HeLa cells using a luciferase reporter driven by a 617-bp minimal promoter containing point mutations in putative regulatory elements. Sp1 and NF-Y were both found to be transcriptional modulators with activator or repressor functions depending on protein/DNA context. Moreover, a functional interaction between Sp1 and NF-Y bound at proximal elements was observed.

• Authors: Natisha Magan, Agnieszka P Szremska, Richard J Isaacs, Kathryn M Stowell
• Journal: The Biochemical journal (Biochem J) Vol. 374 Issue Pt 3 Pg. 723-9 (Sep 15 2003) ISSN: 1470-8728 [Electronic] England
• PMID: 12769819 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, Neoplasm
• CCAAT-Binding Factor
• DNA-Binding Proteins
• Recombinant Fusion Proteins
• Sp1 Transcription Factor
• Transcription Factors
• nuclear factor Y
• Sp2 Transcription Factor
• Luciferases
• DNA Topoisomerases, Type II

Topics

• Antigens, Neoplasm
• CCAAT-Binding Factor (genetics, physiology)
• DNA Topoisomerases, Type II (genetics, metabolism)
• DNA-Binding Proteins (genetics, metabolism, physiology)
• Electrophoretic Mobility Shift Assay
• Gene Expression Regulation, Enzymologic
• Genes, Reporter (genetics)
• HeLa Cells
• Humans
• Luciferases (genetics)
• Mutagenesis, Site-Directed
• Promoter Regions, Genetic
• Recombinant Fusion Proteins (genetics)
• Sp1 Transcription Factor (genetics, physiology)
• Sp2 Transcription Factor
• Transcription Factors (genetics, physiology)
• Transfection
• Tumor Cells, Cultured