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 M_r 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 S_20,W of 21S on sucrose gradients. They are immunologically similar in several human cell lines.