title: A telomerase-independent component of telomere loss in chromatin assembly factor 1 mutants of Arabidopsis thaliana.
abstract: Dysfunction of chromatin assembly factor 1 in FASCIATA mutants (fas) of Arabidopsis thaliana results in progressive loss of telomeric DNA. Although replicative telomere shortening is typically associated with incomplete resynthesis of their ends by telomerase, no change in telomerase activity could be detected in vitro in extracts from fas mutants. Besides a possible telomerase malfunction, the telomere shortening in fas mutants could presumably be due to problems with conventional replication of telomeres. To distinguish between the possible contribution of suboptimal function of telomerase in fas mutants under in vivo conditions and problems in conventional telomere replication, we crossed fas and tert (telomerase reverse transcriptase) knockout mutants and analyzed telomere shortening in segregated fas mutants, tert mutants, and double fas tert mutants in parallel. We demonstrate that fas tert knockouts show greater replicative telomere shortening than that observed even in the complete absence of telomerase (tert mutants). While the effect of tert and fas mutations on telomere lengths in double mutants is additive, manifestations of telomere dysfunction in double fas tert mutants (frequency of anaphase bridges, onset of chromosome end fusions, and common involvement of 45S rDNA in chromosome fusion sites) are similar to those in tert mutants. We conclude that in addition to possible impairment of telomerase action, a further mechanism contributes to telomere shortening in fas mutants.
authors.affiliation: Central European Institute of Technology (CEITEC) and Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic.
authors.forename: Karin
authors.initials: K
authors.lastname: Jaške
authors.forename: Petr
authors.initials: P
authors.lastname: Mokroš
authors.forename: Iva
authors.initials: I
authors.lastname: Mozgová
authors.forename: Miloslava
authors.initials: M
authors.lastname: Fojtová
authors.forename: Jiří
authors.initials: J
authors.lastname: Fajkus
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D056504:Chromatin Assembly Factor-1 / Q000235:genetics / Q000378:metabolism; D032461:Chromosomes, Plant / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D000072260:RNA Splicing Factors; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C518085:At2g20020 protein, Arabidopsis; D056504:Chromatin Assembly Factor-1; C422044:FAS protein, Arabidopsis; D000072260:RNA Splicing Factors; C528255:TERT protein, Arabidopsis; D019098:Telomerase
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