title: Transcription of ribosomal genes can cause nondisjunction.
abstract: Mitotic disjunction of the repetitive ribosomal DNA (rDNA) involves specialized segregation mechanisms dependent on the conserved phosphatase Cdc14. The reason behind this requirement is unknown. We show that rDNA segregation requires Cdc14 partly because of its physical length but most importantly because a fraction of ribosomal RNA (rRNA) genes are transcribed at very high rates. We show that cells cannot segregate rDNA without Cdc14 unless they undergo genetic rearrangements that reduce rDNA copy number. We then demonstrate that cells with normal length rDNA arrays can segregate rDNA in the absence of Cdc14 as long as rRNA genes are not transcribed. In addition, our study uncovers an unexpected role for the replication barrier protein Fob1 in rDNA segregation that is independent of Cdc14. These findings demonstrate that highly transcribed loci can cause chromosome nondisjunction.
authors.affiliation: Cell Cycle Group, Medical Research Council Clinical Sciences Centre, Imperial College London, London W12 0NN, England, UK.
authors.forename: Felix
authors.initials: F
authors.lastname: Machín
authors.forename: Jordi
authors.initials: J
authors.lastname: Torres-Rosell
authors.forename: Giacomo
authors.initials: G
authors.lastname: De Piccoli
authors.forename: Jesús A
authors.initials: JA
authors.lastname: Carballo
authors.forename: Rita S
authors.initials: RS
authors.lastname: Cha
authors.forename: Adam
authors.initials: A
authors.lastname: Jarmuz
authors.forename: Luis
authors.initials: L
authors.lastname: Aragón
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology; D020090:Chromosome Segregation; D004275:DNA, Ribosomal / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D005785:Gene Conversion / Q000502:physiology; D017353:Gene Deletion; D018628:Gene Dosage; D018816:Genes, cdc; D020459:Genes, rRNA; D008957:Models, Genetic; D009154:Mutation; D009630:Nondisjunction, Genetic; D012319:RNA Polymerase II / Q000378:metabolism; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000502:physiology*; D015003:Yeasts / Q000166:cytology
chemical_list: D018797:Cell Cycle Proteins; D004275:DNA, Ribosomal; D005656:Fungal Proteins; D012335:RNA, Ribosomal; D012319:RNA Polymerase II