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Molecular and Cellular Biology, May 2008, p. 2872-2883, Vol. 28, No. 9
0270-7306/08/$08.00+0 doi:10.1128/MCB.02181-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Frédéric Catez,1,2,
Gabi Gerlitz,1 and
Michael Bustin1*
Protein Section, Laboratory of Metabolism, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892,1 Université Lyon 1, Lyon F-69003, and CNRS, UMR5534, Centre de Génétique Moléculaire et Cellulaire, Villeurbanne F-69622, France2
Received 10 December 2007/ Returned for modification 6 February 2008/ Accepted 15 February 2008
Numerous nuclear proteins bind to chromatin by targeting unique DNA sequences or specific histone modifications. In contrast, HMGN proteins recognize the generic structure of the 147-bp nucleosome core particle. HMGNs alter the structure and activity of chromatin by binding to nucleosomes; however, the determinants of the specific interaction of HMGNs with chromatin are not known. Here we use systematic mutagenesis, quantitative fluorescence recovery after photobleaching, fluorescence imaging, and mobility shift assays to identify the determinants important for the specific binding of these proteins to both the chromatin of living cells and to purified nucleosomes. We find that several regions of the protein affect the affinity of HMGNs to chromatin; however, the conserved sequence RRSARLSA, is the sole determinant of the specific interaction of HMGNs with nucleosomes. Within this sequence, each of the 4 amino acids in the R-S-RL motif are the only residues absolutely essential for anchoring HMGN protein to nucleosomes, both in vivo and in vitro. Our studies identify a new chromatin-binding module that specifically recognizes nucleosome cores independently of DNA sequence or histone tail modifications.
Published ahead of print on 25 February 2008.
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