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Open Access Highly Accessed Research article

Contribution of nucleosome binding preferences and co-occurring DNA sequences to transcription factor binding

Ximiao He1, Raghunath Chatterjee1, Sam John26, Hector Bravo5, B K Sathyanarayana3, Simon C Biddie2, Peter C FitzGerald4, John A Stamatoyannopoulos6, Gordon L Hager2 and Charles Vinson1*

Author Affiliations

1 Laboratory of Metabolism, National Cancer Institute, National Institutes of Health, Room 3128, Building 37, 37 Convent Drive, Bethesda, MD 20892, USA

2 Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, B602, Building 41, 41 Library Drive, Bethesda, MD 20892, USA

3 Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA

4 Genome Analysis Unit, Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA

5 Center for Bioinformatics and Computational Biology, Biomolecular Sciences Bldg #296, University of Maryland, College Park, MD 20742, USA

6 Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA

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BMC Genomics 2013, 14:428  doi:10.1186/1471-2164-14-428

Published: 28 June 2013

Abstract

Background

Chromatin plays a critical role in regulating transcription factors (TFs) binding to their canonical transcription factor binding sites (TFBS). Recent studies in vertebrates show that many TFs preferentially bind to genomic regions that are well bound by nucleosomes in vitro. Co-occurring secondary motifs sometimes correlated with functional TFBS.

Results

We used a logistic regression to evaluate how well the propensity for nucleosome binding and co-occurrence of a secondary motif identify which canonical motifs are bound in vivo. We used ChIP-seq data for three transcription factors binding to their canonical motifs: c-Jun binding the AP-1 motif (TGAC/GTCA), GR (glucocorticoid receptor) binding the GR motif (G-ACA---T/CGT-C), and Hoxa2 (homeobox a2) binding the Pbx (Pre-B-cell leukemia homeobox) motif (TGATTGAT). For all canonical TFBS in the mouse genome, we calculated intrinsic nucleosome occupancy scores (INOS) for its surrounding 150-bps DNA and examined the relationship with in vivo TF binding. In mouse mammary 3134 cells, c-Jun and GR proteins preferentially bound regions calculated to be well-bound by nucleosomes in vitro with the canonical AP-1 and GR motifs themselves contributing to the high INOS. Functional GR motifs are enriched for AP-1 motifs if they are within a nucleosome-sized 150-bps region. GR and Hoxa2 also bind motifs with low INOS, perhaps indicating a different mechanism of action.

Conclusion

Our analysis quantified the contribution of INOS and co-occurring sequence to the identification of functional canonical motifs in the genome. This analysis revealed an inherent competition between some TFs and nucleosomes for binding canonical TFBS. GR and c-Jun cooperate if they are within 150-bps. Binding of Hoxa2 and a fraction of GR to motifs with low INOS values suggesting they are not in competition with nucleosomes and may function using different mechanisms.

Keywords:
TFBS; Nucleosome; GR; c-Jun