Nucleolar Preribosomal Associated Protein 2 (NPA2)

NPA2 required for 27S pre-rRNA processing. Has an early role during 60S ribosomal subunit assembly. Proteins of isolated 80-S and 60-S nucleolar preribosomal particles were characterized by means of two-dimensional polyacrylamide gel electrophoresis, in the lymphocytic mouse leukemia cells L5178Y. Their identification and metabolic relationships with ribosomal subunit proteins were investigated using co-electrophoresis of unlabeled polysomal proteins with labeled proteins of either nucleolar preribosomes or ribosomal subunits. The large and small ribosomal subunits contain 40 and 31 proteins, respectively. The nucleolar 80-S preribosomes were analysed after 2 and 5 h of incubation with tritiated valine and leucine and were shown to contain about 55 proteins. Most of them were identical to cytoplasmic ribosomal subunit proteins.