title: Identification and characterization of an essential telomeric repeat binding factor in fission yeast.
abstract: Whereas mammalian cells harbor two double strand telomeric repeat binding factors, TRF1 and TRF2, the fission yeast Schizosaccharomyces pombe has been thought to harbor solely the TRF1/TRF2 ortholog Taz1p to perform comparable functions. Here we report the identification of telomeric repeat binding factor 1 (Tbf1), a second TRF1/TRF2 ortholog in S. pombe. Like the Taz1p, the identified Tbf1p shares amino acid sequence similarity, as well as structural and functional characteristics, with the mammalian TRF1 and TRF2 proteins. This family of proteins shares a common architecture with two separate structural domains. An N-terminal domain is necessary and sufficient for the formation of homodimers, and a C-terminal MYB/homeodomain mediates sequence specific recognition of double-stranded telomeric DNA. The identified Tbf1p binds S. pombe telomeric DNA with high sequence specificity in vitro. Targeted deletion of the tbf1 gene reveals that it is essential for survival, and overexpression of the tbf1 gene leads to telomere elongation in vivo, which is dependent upon the MYB domain. These data suggest that fission yeast, like mammals, have two factors that bind double-stranded telomeric DNA and perform distinct roles in telomere length regulation.
authors.affiliation: Telomere Biology Laboratory, Cancer Research UK, London, United Kingdom.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Pitt
authors.forename: Luis P
authors.initials: LP
authors.lastname: Valente
authors.forename: Daniela
authors.initials: D
authors.lastname: Rhodes
authors.forename: Tomas
authors.initials: T
authors.lastname: Simonsson
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D018390:Gene Targeting; D005800:Genes, Fungal; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D016615:Telomere / Q000378:metabolism; D035321:Telomeric Repeat Binding Protein 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D035321:Telomeric Repeat Binding Protein 1