title: The ubiquitin-activating enzyme (E1) of the early-branching eukaryote Giardia intestinalis shows unusual proteolytic modifications and play important roles during encystation.
abstract: Giardia intestinalis is considered an early-branching eukaryote and is therefore a valuable model for studying primordial cellular processes. This work reports the characterization of the ubiquitin-activating enzyme (E1) during growth and different stages of trophozoite differentiation into cysts. We found that in Giardia E1 expression (both at mRNA and protein levels) is regulated during encystation. The enzyme is proteolytically processed mainly into two fragments of 68kDa (N-terminal) and 47kDa (C-terminal). This phenomenon has not been described for any other E1. In trophozoites, this enzyme localized at spots within the cytoplasm as detected by using polyclonal antibodies against either E1 N- or C-terminal fragments. This pattern changed during encystation into a diffuse localization throughout the cytoplasm of encysting cells. E1 localizes in mature cysts at cytoplasmic spots and in the cyst wall. Our antisense silencing experiments suggested that E1 is an essential gene for parasite viability. On the other hand, E1 over-expression greatly increased the encystation rate, indicating a relationship between E1 and Giardia differentiation.
authors.affiliation: Laboratory of Basic Research in Biochemistry - LIBBIQ, Departamento de Química, Universidad Nacional de Colombia, Bogotá, Colombia.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Niño
authors.forename: Cesar G
authors.initials: CG
authors.lastname: Prucca
authors.forename: Jenny
authors.initials: J
authors.lastname: Chaparro
authors.forename: Hugo D
authors.initials: HD
authors.lastname: Luján
authors.forename: Moisés
authors.initials: M
authors.lastname: Wasserman
mesh_terms: D000818:Animals; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D016829:Giardia lamblia / Q000201:enzymology* / Q000254:growth & development*; D051379:Mice; D008807:Mice, Inbred BALB C; D050296:Microbial Viability; D059748:Proteolysis; D033761:Spores, Protozoan / Q000201:enzymology / Q000254:growth & development; D053058:Trophozoites / Q000201:enzymology / Q000254:growth & development; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism*
chemical_list: D044764:Ubiquitin-Activating Enzymes