Dual function of a nuclear factor I binding site in MMTV transcription regulation.
Using linker-scanning mutagenesis we had previously identified four elements within the MMTV LTR which are necessary for transcriptional stimulation by glucocorticoid hormones. Two of them overlapped with regions to which the glucocorticoid receptor binds in vitro. The third element contained a NF-I binding site, and the fourth the TATA box. Here we show that mutations that abolish in vitro binding of NF-I had a negative effect also on the basal activity of the MMTV promoter of LTR-containing plasmids stably integrated in Ltk- fibroblasts. The analysis of double mutants altered in the NF-I plus either one of the receptor binding elements further demonstrated that the NF-I site functionally cooperated with the proximal (-120) element, which alone was extremely inefficient in stimulation. The stronger distal (-181/-172) element was independent of NF-I and showed functional cooperativity with the proximal hormone-binding element.
Buetti
E
E
Swiss Institute for Experimental Cancer Research, Epalinges.
Kühnel
B
B
Diggelmann
H
H
D000818:Animals; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007739:L Cells; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D051379:Mice; D051839:NFI Transcription Factors; D009687:Nuclear Proteins / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011965:Receptors, Glucocorticoid / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D051840:Y-Box-Binding Protein 1
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D003907:Dexamethasone