title: Differential arrival of leading and lagging strand DNA polymerases at fission yeast telomeres.
abstract: To maintain genomic integrity, telomeres must undergo switches from a protected state to an accessible state that allows telomerase recruitment. To better understand how telomere accessibility is regulated in fission yeast, we analysed cell cycle-dependent recruitment of telomere-specific proteins (telomerase Trt1, Taz1, Rap1, Pot1 and Stn1), DNA replication proteins (DNA polymerases, MCM, RPA), checkpoint protein Rad26 and DNA repair protein Nbs1 to telomeres. Quantitative chromatin immunoprecipitation studies revealed that MCM, Nbs1 and Stn1 could be recruited to telomeres in the absence of telomere replication in S-phase. In contrast, Trt1, Pot1, RPA and Rad26 failed to efficiently associate with telomeres unless telomeres are actively replicated. Unexpectedly, the leading strand DNA polymerase epsilon (Polepsilon) arrived at telomeres earlier than the lagging strand DNA polymerases alpha (Polalpha) and delta (Poldelta). Recruitment of RPA and Rad26 to telomeres matched arrival of DNA Polepsilon, whereas S-phase specific recruitment of Trt1, Pot1 and Stn1 matched arrival of DNA Polalpha. Thus, the conversion of telomere states involves an unanticipated intermediate step where lagging strand synthesis is delayed until telomerase is recruited.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA.
authors.forename: Bettina A
authors.initials: BA
authors.lastname: Moser
authors.forename: Lakxmi
authors.initials: L
authors.lastname: Subramanian
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Chang
authors.forename: Chiaki
authors.initials: C
authors.lastname: Noguchi
authors.forename: Eishi
authors.initials: E
authors.lastname: Noguchi
authors.forename: Toru M
authors.initials: TM
authors.lastname: Nakamura
mesh_terms: D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D004256:DNA Polymerase I / Q000378:metabolism; D004260:DNA Repair; D004261:DNA Replication; D004271:DNA, Fungal / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004271:DNA, Fungal; C478035:Nbs1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; C088086:rad26 protein, S pombe; D019098:Telomerase; D004256:DNA Polymerase I; D004259:DNA-Directed DNA Polymerase