Cloning of Dictyostelium eIF6 (p27BBP) and mapping its nucle(ol)ar localization subdomains.
Eukaryotic translation initiation factor 6 (eIF6), also termed p27BBP, is an evolutionary conserved regulator of ribosomal function. The protein is involved in maturation and/or export from the nucleus of the 60S ribosomal subunit. Regulated binding to and release from the 60S subunit also regulates formation of 80S ribosomes, and thus translation. The protein is also found in hemidesmosomes of epithelial cells expressing beta4 integrin and is assumed to regulate cross-talk between beta4 integrin, intermediate filaments and ribosomes. In the present study we show that the Dictyostelium eIF6 (also called p27BBP) gene is expressed during growth, down-regulated during the first hours of starvation, and up-regulated again at the end of aggregation. Phagocytosis, and to a lesser extent pinocytic uptake of axenic medium, stimulate gene expression in starving cells. The eIF6 gene is present in single copy and its ablation is lethal. We utilized the green fluorescent protein (GFT) as fusion protein marker to investigate sequences responsible for eIF6 subcellular localization. The protein is found both in cytoplasm and nucleus, and is enriched in nucleoli. Deletion sequence analysis shows that nucle(ol)ar localization sequences are located within the N- and C-terminal subdomains of the protein.
Balbo
Alessandra
A
Department of Clinical and Biological Sciences, University of Turin, Ospedale S. Luigi, I-10043 Orbassano, Italy.
Bozzaro
Salvatore
S
D000595:Amino Acid Sequence; D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism* / Q000648:ultrastructure; D003609:Dactinomycin / Q000494:pharmacology; D004023:Dictyostelium / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D039642:Eukaryotic Initiation Factors / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008969:Molecular Sequence Data; D010448:Peptide Initiation Factors / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D016415:Sequence Alignment
D039642:Eukaryotic Initiation Factors; D010448:Peptide Initiation Factors; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D003609:Dactinomycin