A divalent switch drives H-NS/DNA-binding conformations between stiffening and bridging modes

Genes Dev. 2010 Feb 15;24(4):339-44. doi: 10.1101/gad.1883510.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacterial Proteins / metabolism*
  • Cations, Divalent*
  • DNA, Bacterial / chemistry*
  • DNA, Bacterial / metabolism*
  • DNA-Binding Proteins / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Gene Silencing
  • Hydrogen-Ion Concentration
  • Magnesium Chloride / pharmacology
  • Nucleic Acid Conformation
  • Polymers / metabolism
  • Protein Binding / drug effects
  • Salmonella / genetics*
  • Salmonella / metabolism*
  • Temperature

Substances

  • Bacterial Proteins
  • Cations, Divalent
  • DNA, Bacterial
  • DNA-Binding Proteins
  • H-NS protein, bacteria
  • Polymers
  • Magnesium Chloride