A novel component involved in ubiquitination is required for development of Dictyostelium discoideum.
A novel component of the ubiquitination system, called NOSA, is essential for cellular differentiation in Dictyostelium discoideum. Disruption of nosA does not affect the growth rate but causes an arrest in development after the cells have aggregated. nosA contains seven exons and codes for a developmentally regulated 3.5-kb mRNA. The 125-kDa NOSA protein is present in the cytosol at constant levels during growth and development. The C-terminal region of NOSA has homology with ubiquitin fusion degradation protein-2 (UFD2) of Saccharomyces cerevisiae and putative homologs in Caenorhabditis elegans and humans. UFD2 is involved in the ubiquitin-mediated degradation of model substrates in which ubiquitin forms part of the translation product, but ufd2 mutants have no detected phenotype. In accord with the homology to UFD2, we found differences in the ubiquitination patterns between nosA mutants and their parental cell line. While general in vivo and in vitro ubiquitination is minimally affected, ubiquitination of individual proteins is altered throughout growth and development in nosA mutants. These findings suggest that events involving ubiquitination are critical for progression through the aggregate stage of the Dictyostelium life cycle.
Pukatzki
S
S
Department of Anatomy and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Tordilla
N
N
Franke
J
J
Kessin
R H
RH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics; D003600:Cytosol / Q000378:metabolism; D004023:Dictyostelium / Q000235:genetics* / Q000254:growth & development* / Q000648:ultrastructure; D005091:Exons; D005656:Fungal Proteins / Q000737:chemistry; D018507:Gene Expression Regulation, Developmental; D005800:Genes, Fungal; D006801:Humans; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D044763:Ubiquitin-Conjugating Enzymes; D014452:Ubiquitins / Q000378:metabolism*
D005656:Fungal Proteins; C114687:NOSA protein, Dictyostelium discoideum; D015800:Protozoan Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; D044763:Ubiquitin-Conjugating Enzymes; C114683:UFD2 protein, S cerevisiae