DNA-protein complexes of the nuclear matrix: visualization and partial characterization of the protein component

Complexes composed of DNA attached to the nuclear matrix and of proteins most tightly bound to DNA are visualized as globular particles 25-35 nm in diameter. Their morphology depends greatly on the isolation conditions: a Cs salts/urea combination permits the isolation while CsCl/sarcosyl destroys the particles. The preparation is shown to have the same protein content regardless of the treatment employed. The proteins of the complex are resistant to SDS and pronase treatment and to phenol/chloroform extraction while being associated with DNA.