title: Identification and expression of the protein ubiquitination system in Giardia intestinalis.
abstract: Giardia intestinalis is a single-cell eukaryotic microorganism, regarded as one of the earliest divergent eukaryotes and thus an attractive model to study the evolution of regulatory systems. Giardia has two different forms throughout its life cycle, cyst and trophozoite, and changes from one to the other in response to environmental signals. The two differentiation processes involve a differential gene expression as well as a quick and specific protein turnover that may be mediated by the ubiquitin/proteasome system. The aim of this work was to search for unreported components of the ubiquitination system and to experimentally demonstrate their expression in the parasite and during the two differentiation processes. We found activity of protein ubiquitination in G. intestinalis trophozoites and analyzed the transcription of the ubiquitin gene, as well as that of the activating (E1), conjugating (E2), and ligase (E3) ubiquitin enzymes during encystation and excystation. A constant ubiquitin expression persisted during the parasite's differentiation processes, whereas variation in transcription was observed in the other genes under study.
authors.affiliation: Laboratorio de Investigaciones Básicas en Bioquímica, Facultad de Ciencias, Universidad Nacional de Colombia, Unidad Camilo Torres Cra 50 No 27-70 Bloque 10 nivel 4, Bogota, Colombia.
authors.forename: Eva
authors.initials: E
authors.lastname: Gallego
authors.forename: Magda
authors.initials: M
authors.lastname: Alvarado
authors.forename: Moises
authors.initials: M
authors.lastname: Wasserman
mesh_terms: D000818:Animals; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D018503:Genome, Protozoan / Q000235:genetics; D016829:Giardia lamblia / Q000235:genetics*; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; D044764:Ubiquitin-Activating Enzymes