Cytoplasmic extraction: polyribosomes and heterogenous ribonucleoproteins without associated DNA

Two methods are described for preparing cytoplasmic extracts from sea urchin embryos. One method, involving homogenization, yields DNA structures that cosediment with polyribosomes and subribosomal ribonucleoproteins. In addition this method also yields extraneous structures containing RNA that cosediment with polyribosomes. The DNA is not associated with polyribosomes, as shown by buoyant density analysis. Furthermore, this DNA appears to be spurious, because its release into a cytoplasmic extract does not occur when a different method of cell disruption, involving passage of embryos through a hypodermic needle, is used. With this second method, polyribosomes are obtained without extraneous cosedimenting RNA structures and subribosomal ribonucleo-proteins are obtained in the virtual absence of DNA.