Metabolism of ribosomal proteins microinjected into the oocytes of Xenopus laevis

Journal Article · Fri Jan 01 04:00:00 EST 1988 · Exp. Cell Res.; (United States)

DOI:https://doi.org/10.1016/0014-4827(88)90153-X· OSTI ID:5600611

Tsurugi, K; Motizuki, M; Mitsui, K; Endo, Y; Shiokawa, K

When the total proteins from Xenopus laevis 60 S ribosomal subunits (TP60) were /sup 3/H-labeled in vitro and injected back into X. laevis oocytes, most /sup 3/H-TP60 are integrated into the cytoplasmic 60 S subunits via the nucleus during 16 h of incubation. In the oocytes whose rRNA synthesis is inhibited, /sup 3/H-TP60 are rapidly degraded with a half-life of 2-3 h. This degradation ceased as soon as rRNA synthesis was resumed, suggesting that ribosomal proteins unassociated with nascent rRNA are unstable in the oocytes. The degradation of /sup 3/H-TP60 in the absence of RNA synthesis was inhibited by iodoacetamide, a cysteine protease inhibitor, resulting in the accumulation of /sup 3/H-TP60 in the nucleus reaching about a threefold concentration in the cytoplasm. Considering the results with enucleated oocytes, we suggest that the X. laevis nucleus has a limited capacity to accumulate ribosomal proteins in an active manner but that those ribosomal proteins accumulated in excess over rRNA synthesis are degraded by a cysteine protease in the nucleus. By contrast, ribosomal proteins from Escherichia coli only equilibrate between the nucleus and the cytoplasm and are degraded by serine protease(s) in the cytoplasm without being integrated in the form of ribosomes in the nucleus.

• Research Organization: Yamanashi Medical College, Japan
• OSTI ID: 5600611
• Journal Information: Exp. Cell Res.; (United States), Journal Name: Exp. Cell Res.; (United States) Vol. 174:1; ISSN ECREA
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMPHIBIANS
ANIMALS
AQUATIC ORGANISMS
AZINES
BACTERIA
BIOLOGICAL HALF-LIFE
BIOSYNTHESIS
BOROHYDRIDES
BORON COMPOUNDS
CELL CONSTITUENTS
CELL NUCLEI
CYTOPLASM
ENZYME INHIBITORS
ENZYMES
ESCHERICHIA COLI
FROGS
GERM CELLS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
INHIBITION
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
METABOLISM
MICROORGANISMS
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
OOCYTES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDE HYDROLASES
PROTEINS
PYRIMIDINES
RIBOSIDES
RIBOSOMAL RNA
RNA
SERINE PROTEINASES
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
URACILS
URIDINE
VERTEBRATES