STUDIES ON NUCLEOLAR AND RIBOSOMAL BASIC PROTEINS AND THEIR RELATIONSHIP TO NUCLEOLAR FUNCTION

The study presented here demonstrates electrophoretic similarity between the basic protein of rat liver ribosomal protein and starfish oocyte ribosomal protein. This suggests some species-independence of at least a portion of the ribosomal proteins. In addition, electrophoretic similarity exists between the basic proteins of rat liver ribosomes and nucleoli. This, combined with earlier studies, suggests that the nucleolus contains a number of basic proteins whose molecular species are very much like those of cytoplasmic ribosomes. The structure of the nucleolus is interpreted as consisting of (1) a core of material containing basic proteins which are capable of complexing with newly synthesized RNA to form the basis of the ribosome, and (2) a cortical region containing newly formed ribosomes destined to leave the nucleolus for other cellular sites. © 1968.