Purification and partial characterization of ring-shaped miniparticles

Small ring-shaped miniparticles, found in the nucleus nucleolus and cytoplasm of a variety of normal and malignant cells, have been purified by a procedure involving differential and gradient centrifugation, hydroxylapatite chromatography and preparative electrophoresis. They are multisubunit proteins comprised of at least six polypeptide chains of Mr 20,000-30,000 Daltons (by one-D SDS-PAGE which present a series of 20-30 spots on two-D IEF/SDS gels. They can be reversibly dissociated in EDTA containing buffers. They are not membrane associated and contain no carbohydrate. They have an S20,W of 21S on sucrose gradients. They are immunologically similar in several human cell lines.