METABOLISM AND MORPHOLOGY OF RIBONUCLEOPROTEIN PARTICLES FROM THE CELL NUCLEUS OF LYMPHOCYTES

Abstract

Ribonucleoprotein particles can be extracted by neutral buffer solutions from isolated nuclei of calf thymus lymphocytes. Such particles can be fractionated and characterized by their ease of extraction, their sedimentability, their protein and RNA composition, and by their rate of protein and RNA metabolism in the nucleus. The rates of protein and of RNA metabolism in the nucleus are parallel in each class of particles. The particles are revealed by electron micrography to consist of elementary units of 15-25 A diameter, arranged in rings or clusters. Metabolic evidence suggests that certain of the classes of isolated particles may be derived from the nucleus. Isolated particles extracted from the cell nucleus remain capable of incorporating radioactive precursors into their constituent proteins in a nucleus-free system.