title: Est1 and Cdc13 as comediators of telomerase access.
abstract: Cdc13 and Est1 are single-strand telomeric DNA binding proteins that contribute to telomere replication in the yeast Saccharomyces cerevisiae. Here it is shown that fusion of Cdc13 to the telomerase-associated Est1 protein results in greatly elongated telomeres. Fusion proteins consisting of mutant versions of Cdc13 or Est1 confer similar telomere elongation, indicating that close physical proximity can bypass telomerase-defective mutations in either protein. Fusing Cdc13 directly to the catalytic core of telomerase allows stable telomere maintenance in the absence of Est1, consistent with a role for Est1 in mediating telomerase access. Telomere length homeostasis therefore is maintained in part by restricting access of telomerase to chromosome termini, but this limiting situation can be overcome by directly tethering telomerase to the telomere.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Evans
authors.forename: V
authors.initials: V
authors.lastname: Lundblad
mesh_terms: D001665:Binding Sites; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D004271:DNA, Fungal / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D006706:Homeostasis; D008954:Models, Biological; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism*
chemical_list: D019926:Cyclin B; D004271:DNA, Fungal; D004277:DNA, Single-Stranded; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C099024:EST1 protein, S cerevisiae; D019098:Telomerase