PMID: 2498322May 25, 1989Paper

fos/jun and octamer-binding protein interact with a common site in a negative element of the human c-myc gene

The Journal of Biological Chemistry
M TakimotoD Levens

Abstract

A negative element has previously been localized to a 57-base pair segment approximately 300 base pairs upstream of the human c-myc promoter P1. Within this element, a 26-base pair region was protected in vitro from DNase I digestion with a HeLa cell nuclear factor(s). Two specific DNA-protein complexes were identified in gel retardation assays using HeLa cell nuclear extracts and an oligonucleotide probe spanning the footprinted region. Exonuclease and chemical footprint analyses suggested that the binding sites for both complexes are almost entirely overlapping. One of the complexes was eliminated by oligonucleotide competitors possessing known AP-1 binding sites. This same complex reacted strongly with anti-fos immunoglobulin suggesting a role for c-fos in governing c-myc expression. Precipitation of fos protein bound to c-myc DNA that was immobilized on beads confirmed the involvement of c-fos in a specific complex with the c-myc upstream sequence. In contrast, the other complex seen by the c-myc probe could not be competitively inhibited by AP-1 binding sites and was not affected by anti-fos antibody. Instead, this complex was efficiently eliminated by unlabeled oligonucleotides containing the octamer DNA motif found in im...Continue Reading

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