Constitutive expression of the Id-1 promoter in human metastatic breast cancer cells is linked with the loss of NF-1/Rb/HDAC-1 transcription repressor complex.
The helix-loop-helix protein Id-1 is a dominant negative regulator of basic helix-loop-helix transcription factors, and plays a key role in the control of breast epithelial cell growth, invasion and differentiation. Previous investigations in our laboratory have shown that Id-1 mRNA was constitutively expressed in highly aggressive and invasive human breast ... cancer cells in comparison to non-transformed or non-aggressive cancerous cells, and that this loss of regulation is mediated by a 2.2-kb region of the human Id-1 promoter. Here we show that a 31 bp sequence within this 2.2-kb promoter, located 200 bp upstream of the initiation of transcription, is responsible for the constitutive expression of Id-1 in metastatic human breast cancer cells. Using gel shift experiments, we identified a high molecular weight complex present only in non-aggressive breast cancer cells cultured in serum-free medium and which appear to be necessary for proper Id-1 repression. In contrast, nuclear extracts from highly aggressive and metastatic cell lines do not contain this large molecular weight complex. Using DNA affinity precipitation assays (DAPA), we show that this complex contains SP-1, NF-1, Rb and HDAC-1 proteins. On the basis of these findings, we propose a mechanism for the loss of regulation of Id-1 promoter in invasive and metastatic human breast cancer cells.
Mesh Terms:
Binding Sites, Blotting, Western, Breast Neoplasms, DNA Primers, DNA, Neoplasm, DNA-Binding Proteins, Electrophoretic Mobility Shift Assay, Epithelial Cells, Female, Gene Deletion, Gene Expression Regulation, Neoplastic, Helix-Loop-Helix Motifs, Histone Deacetylase 1, Histone Deacetylases, Humans, Inhibitor of Differentiation Protein 1, Mutation, Neoplasm Invasiveness, Neurofibromin 1, Plasmids, Podophyllin, Podophyllotoxin, Precipitin Tests, Promoter Regions, Genetic, Repressor Proteins, Retinoblastoma Protein, Transcription Factors, Transfection, Tumor Cells, Cultured
Binding Sites, Blotting, Western, Breast Neoplasms, DNA Primers, DNA, Neoplasm, DNA-Binding Proteins, Electrophoretic Mobility Shift Assay, Epithelial Cells, Female, Gene Deletion, Gene Expression Regulation, Neoplastic, Helix-Loop-Helix Motifs, Histone Deacetylase 1, Histone Deacetylases, Humans, Inhibitor of Differentiation Protein 1, Mutation, Neoplasm Invasiveness, Neurofibromin 1, Plasmids, Podophyllin, Podophyllotoxin, Precipitin Tests, Promoter Regions, Genetic, Repressor Proteins, Retinoblastoma Protein, Transcription Factors, Transfection, Tumor Cells, Cultured
Oncogene
Date: Mar. 14, 2002
PubMed ID: 11896613
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