title: Characterization of telomeres and telomerase from the single-celled eukaryote Giardia intestinalis.
abstract: The ends of linear chromosomes, telomeres, are most commonly maintained by the enzyme telomerase. Our study presents the characteristics of telomeres and telomerase from the single-celled parasitic eukaryote Giardia intestinalis. Using fluorescence in situ hybridization, we localized telomeres during all stages of the trophozoite cell cycle and demonstrated differences in the observed number of telomeric foci, indicating telomere clustering. The length of Giardia telomeres was determined in different cell lines derived from WB clinical isolate using terminal restriction fragment analysis and ranged from 0.5 to 2.5kb; moreover, a BAL-31 digestion experiment did not reveal any long interstitial telomeric sequences in the genome. Despite the absence of the specific T motif in the telomerase catalytic subunit, the presence of an active telomerase enzyme synthesising telomeric repeats in Giardia was proved by a Telomere repeat amplification protocol assay, and its localization in nuclei was determined by the expression of recombinant GiTERT. Except for the Giardia-type TAGGG telomeric repeat, Giardia telomerase was proved to synthesize in vitro also other repeat variants, TAAGG and TAAGGG. In summary, despite its unusual characteristics, including a structurally divergent but active telomerase, unique terminal sequences and relatively short telomeres, the present data support the view that the chromosomal termini in Giardia are maintained in a conservative manner that is common to other eukaryotes.
authors.affiliation: Department of Tropical Medicine, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Uzlíková
authors.affiliation: Institute of Biophysics, Czech Academy of Sciences, Brno, Czech Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Fulnečková
authors.affiliation: Department of Tropical Medicine, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
authors.forename: Filip
authors.initials: F
authors.lastname: Weisz
authors.affiliation: Institute of Biophysics, Czech Academy of Sciences, Brno, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Sýkorová
authors.affiliation: Department of Tropical Medicine, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Nohýnková
authors.affiliation: Department of Tropical Medicine, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic. Electronic address: ptumo@lf1.cuni.cz.
authors.forename: Pavla
authors.initials: P
authors.lastname: Tůmová
mesh_terms: D002460:Cell Line; D004789:Enzyme Activation; D016829:Giardia lamblia / Q000201:enzymology* / Q000235:genetics*; D005873:Giardiasis / Q000469:parasitology; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008938:Mitosis / Q000235:genetics; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D012091:Repetitive Sequences, Nucleic Acid; D019098:Telomerase / Q000737:chemistry / Q000378:metabolism*; D016615:Telomere / Q000235:genetics*; D059505:Telomere Homeostasis
chemical_list: D021122:Protein Subunits; D019098:Telomerase
keywords: Chromosomes; Giardia; TRAP assay; Telomerase; Telomeres; Terminal restriction fragment