CONFORMATIONAL CHANGES OF SINGLE DNA MOLECULES INDUCED BY H-NS AND HU PROTEINS IN A NANOSPACE

Abstract

THE EFFECTS OF NUCLEOID-ASSOCIATED PROTEINS H-NS AND HU ON THE CONFORMATION OF SINGLE DNA MOLECULES IN A NANOSPACE WERE INVESTIGATED WITH FLUORESCENCE MICROSCOPY. FOR H-NS PROJECT, TEMPORAL CONFORMATION CHANGES WERE ALSO INVESTIGATED USING CROSS CHANNELS. THE CONCENTRATION OF PROTEIN INCREASES, THE DNA-HNS COMPLEX SHOWS AN INCREASE IN LENGTH AT LOW IONIC STRENGTH, AND A DECREASE IN LENGTH AT HIGH IONIC STRENGTH. ON THE OTHER HAND, DNA-HU COMPLEX SHOWS CONTRACTION BY BRIDGING IN HIGH AND LOW IONIC STRENGTH. CONFINEMENT IN A NANOCHANNEL ALSO FACILITATES THE COMPACTION OF DNA INTO A CONDENSED FORM FOR OVER-THRESHOLD CONCENTRATIONS OF PROTEINS. MAGNESIUM FACILITATES BUT ARE NOT REQUIRED FOR BRIDGING NOR CONDENSATION. OUR RESULTS SHOW THAT THE EFFECTS OF NAPS ON THE CONFORMATION AND FOLDING OF DNA DO NOT DEPEND ON DNA-PROTEIN INTERACTION AND CROWDING PER SE, BUT THE INTERPLAY WITH THE CONFINEMENT IN A NANOSPACE SUCH AS WITHIN A BACTERIAL CELL IS OF PARAMOUNT IMPORTANCE.