E. coli DNA binding protein HU forms nucleosomelike structure with circular double-stranded DNA. |
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| Authors: | J Rouvière-Yaniv M Yaniv J E Germond |
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| Institution: | 1. Department of Molecular Biology Pasteur Institute 25, rue du Dr. Roux 75015 Paris, France;2. Laboratory of Electron Microscopy Department of Virology Pasteur Institute 25, rue du Dr. Roux 75015 Paris, France |
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| Abstract: | The incubation of the E coli DNA binding protein HU with relaxed circular SV40 DNA in the presence of pure nicking-closing enzyme introduces up to 18 negative superhelical turns in the DNA molecules as measured by agarose gel electrophoresis. The maximal density of supercoiling is obtained at a HU-DNA mass ratio of 1. Reconstituted DNA-HU complexes prefixed with glutaraldehyde appear as condensed circular structures having an average of 14 "beads" per circular SV40 DNA molecule, with a "bead" diameter of 180 +/- 23 A. The circular SV40 DNA is condensed by a ratio of 2.0-2.5 relative to naked DNA. This is similar to the ratio (2.4) measured for chromatin formed by reassociation of relaxed SV40 DNA with the four core histones. |
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