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Published July 1984 | public
Journal Article

A protein binds to a satellite DNA repeat at three specific sites that would be brought into mutual proximity by DNA folding in the nucleosome


Using a generally applicable assay for specific DNA-binding proteins in crude extracts, we have detected and purified an HMG-like nuclear protein from African green monkey cells that preferentially binds to the 172 bp repeat of α-satellite DNA (α-DNA). DNAase I footprinting with the purified protein detects three specific binding sites (I–III) per α-DNA repeat. Site II is 145 bp (one core nucleosome length) from site III on the adjacent α-DNA repeat, while site I lies midway between sites II and III. In the α-nucleosome phasing frame corresponding with this arrangement, sites I–III would be brought into mutual proximity by DNA folding in the nucleosome. This phasing frame is identical with the preferred frame detected previously in isolated chromatin. Our results suggest that this new and abundant protein recognizes a family of short, related nucleotide sequences found not only in α-DNA but also throughout the genome, and that functions of this protein are mediated through its nucleosome-positioning activity. Such nucleosome-positioning proteins may underlie the sequence specificity of both nucleosome arrangements and higher order chromatin structures.

Additional Information

© 1984 by MIT. Received 4 April 1984, Revised 24 April 1984. We are greatly indebted to Mark Solomon and Louis Levinger for many helpful discussions and advice, and to Daniel Finley and Mark Solomon for their comments on the manuscript. We also thank John Smart (Biogen) for determination of the amino acid composition of o-protein and Ron Rodriguez for his help with protein fractionation. Thus work was supported by grants to A. V. from the National Cancer Institute (CA30367) and from the National Institute of General Medical Sciences (GM31530). F. S. was supported by the Centre National de la Recherche Scientifique (France) and by a Fogarty International Fellowship from the National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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