A divalent switch drives H-NS/DNA-binding conformations between stiffening and bridging modes
- 1Department of Physics, National University of Singapore, Singapore 117542;
- 2Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois 60612, USA;
- 3Department of Biological Sciences, National University of Singapore, Singapore 117543;
- 4Research Centre of Excellence in Mechanobiology, Singapore 117543
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↵5 These authors contributed equally to this work.
Abstract
Heat-stable nucleoid structuring protein (H-NS) is an abundant prokaryotic protein that plays important roles in organizing chromosomal DNA and gene silencing. Two controversial binding modes were identified. H-NS binding stimulating DNA bridging has become the accepted mechanism, whereas H-NS binding causing DNA stiffening has been largely ignored. Here, we report that both modes exist, and that changes in divalent cations drive a switch between them. The stiffening form is present under physiological conditions, and directly responds to pH and temperature in vitro. Our findings have broad implications and require a reinterpretation of the mechanism by which H-NS regulates genes.
Keywords
- Heat-stable nucleoid structuring protein (H-NS)
- gene silencing
- transcriptional regulation
- pathogenicity islands
- atomic force microscopy
- magnetic tweezers
Footnotes
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↵6 Correspondence authors.
E-MAIL kenneyl{at}uic.edu; FAX (312) 413-7339.
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↵7 E-MAIL phyyj{at}nus.edu.sg; FAX 65-6777-6126.
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Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.1883510.
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Supplemental material is available at http://www.genesdev.org.
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- Received November 8, 2009.
- Accepted December 18, 2009.
- Copyright © 2010 by Cold Spring Harbor Laboratory Press
