Chromatin-remodeling enzymes can overcome strong histone-DNA interactions within the nucleosome to regulate access of DNA-binding factors to the genetic code. By unzipping individual DNA duplexes, each containing a uniquely positioned nucleosome flanked by long segments of DNA, we directly probed histone-DNA interactions. The resulting disruption-force signatures were characteristic of the types and locations of interactions and allowed measurement of the positions of nucleosomes with 2.6-base-pair (bp) precision. Nucleosomes remodeled by yeast SWI/SNF were moved bidirectionally along the DNA, resulting in a continuous position distribution. The characteristic distance of motion was approximately 28 bp per remodeling event, and each event occurred with a catalytic efficiency of 0.4 min(-1) per nM SWI/SNF. Remodeled nucleosomes had essentially identical disruption signatures to those of unremodeled nucleosomes, indicating that their overall structure remained canonical. These results impose substantial constraints on the mechanism of SWI/SNF remodeling.

• PMID: 16732285
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Journal Article | Research Support, N.I.H., Extramural | Research Support, Non-U.S. Gov't

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Shundrovsky A, Smith CL, Lis JT, Peterson CL, Wang MD

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