[Composition, structure and various properties of DNA-protein complexes located at the sites of DNA loop attachment...

The intimate structure of the complexes located at the sites of DNA loops attachment to the nuclear skeleton was analysed. It is shown that: there are at least three components of the attachment site complex: DNA, protein, RNA; protein moiety consists of 7-8 species with Mr 70-17 kDa. Their association with DNA is resistant to ionic detergents, high salt and urea treatments. The DNA-protein complex is also resistant to the SDS-pronase-phenol deproteinisation procedure; the buoyant density of the complex is the same as DNA density. RNase digestion at low ionic strength reduces density of the complex while the same treatment at 0,4 M NaCl has no effect; DNA-protein complexes isolated with urea-high salt treatment are visualised as globular particles 25-35 nm in diameter with DNA loops attached. These particles were not observed after detergent treatment although protein composition of the complex remained the same.