[Isolation and comparative characteristics of the DNA attached to the axial structures of interphase nuclei and metaphase chromosomes].

DNA fractions enriched in sequences located closely to the sites of attachment of DNA loops to the axial protein structures of interphase nuclei ad metaphase chromosomes were isolated with the aid of two techniques. The method involving treatment with EcorI endonuclease has been described earlier. The new method is based on the mild treatment of the preparations with micrococcal nuclease. The latter method allows one to obtain the fraction of attached DNA of different length and to compare their properties. The average distance between two attachment sites was measured. It is equal to about 6.10(4) base pairs in the both interphase nuclei and metaphase chromosomes. The attached DNA obtained with the aid of micrococcal nuclease treatment is not enriched in satellite but contains a high amount of middle repetitive sequences renaturing in the Cot interval from 10(-2) to 10(0). According to renaturation properties and distribution in CsCl density gradient the fractions of attached DNA of similar size from metaphase chromosomes and from interphase nuclei are virtually identical. The data obtained indicate that the DNA sequences involved in the attachment of DNA loops to the matrix of interphase nucleus are the same as in the case of metaphase chromosomes.