title: p53 binds preferentially to genomic regions with high DNA-encoded nucleosome occupancy.
abstract: The human transcription factor TP53 is a pivotal roadblock against cancer. A key unresolved question is how the p53 protein selects its genomic binding sites in vivo out of a large pool of potential consensus sites. We hypothesized that chromatin may play a significant role in this site-selection process. To test this, we used a custom DNA microarray to measure p53 binding at approximately 2000 sites predicted to possess high-sequence specificity, and identified both strongly bound and weakly bound sites. When placed within a plasmid, weakly bound sites become p53 responsive and regain p53 binding when stably integrated into random genomic locations. Notably, strongly bound sites reside preferentially within genomic regions whose DNA sequence is predicted to encode relatively high intrinsic nucleosome occupancy. Using in vivo nucleosome occupancy measurements under conditions where p53 is inactive, we experimentally confirmed this prediction. Furthermore, upon p53 activation, nucleosomes are partially displaced from a relatively broad region surrounding the bound p53 sites, and this displacement is rapidly reversed upon inactivation of p53. Thus, in contrast to the general assumption that transcription-factor binding is preferred in sites that have low nucleosome occupancy prior to factor activation, we find that p53 binding occurs preferentially within a chromatin context of high intrinsic nucleosome occupancy.
authors: Department of Molecular Cell Biology, The Weizmann Institute, Rehovot 76100, Israel.
authors: Efrat
authors: E
authors: Lidor Nili
authors: Yair
authors: Y
authors: Field
authors: Yaniv
authors: Y
authors: Lubling
authors: Jonathan
authors: J
authors: Widom
authors: Moshe
authors: M
authors: Oren
authors: Eran
authors: E
authors: Segal
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D016158:Genes, p53; D015894:Genome, Human; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009707:Nucleosomes / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D011485:Protein Binding; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D009707:Nucleosomes; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53