title: Telomere protein Rap1 is a charge resistant scaffolding protein in chromosomal bouquet formation.
abstract: BACKGROUND
  Chromosomes reorganize in early meiotic prophase to form the so-called telomere bouquet. In fission yeast, telomeres localize to the nuclear periphery via interaction of the telomeric protein Rap1 with the membrane protein Bqt4. During meiotic prophase, the meiotic proteins Bqt1-2 bind Rap1 and tether to the spindle pole body to form the bouquet. Although it is known that this polarized chromosomal arrangement plays a crucial role in meiotic progression, the molecular mechanisms of telomere bouquet regulation are poorly understood.
  
  
  RESULTS
  Here, we detected high levels of Rap1 phospho-modification throughout meiotic prophase, and identified a maximum of 35 phosphorylation sites. Concomitant phosphomimetic mutation of the modification sites suggests that Rap1 hyper-phosphorylation does not directly regulate telomere bouquet formation or dissociation. Despite the negative charge conferred by its highly phosphorylated state, Rap1 maintains interactions with its binding partners. Interestingly, mutations that change the charge of negatively charged residues within the Bqt1-2 binding site of Rap1 abolished the affinity to the Bqt1-2 complex, suggesting that the intrinsic negative charge of Rap1 is crucial for telomere bouquet formation.
  
  
  CONCLUSIONS
  Whereas Rap1 hyper-phosphorylation observed in meiotic prophase does not have an apparent role in bouquet formation, the intrinsic negative charge of Rap1 is important for forming interactions with its binding partners. Thus, Rap1 is able to retain bouquet formation under heavily phosphorylated status.
authors.affiliation: Chromosome Maintenance Group, UCL Cancer Institute, University College London, London, WC1E 6DD, UK. h.amelina@ucl.ac.uk.
authors.forename: Hanna
authors.initials: H
authors.lastname: Amelina
authors.affiliation: Chromosome Maintenance Group, UCL Cancer Institute, University College London, London, WC1E 6DD, UK. shaan.subramaniam.10@ucl.ac.uk.
authors.forename: Shaan
authors.initials: S
authors.lastname: Subramaniam
authors.affiliation: Chromosome Maintenance Group, UCL Cancer Institute, University College London, London, WC1E 6DD, UK. v.moiseeva@ucl.ac.uk.
authors.forename: Vera
authors.initials: V
authors.lastname: Moiseeva
authors.affiliation: Chromosome Maintenance Group, UCL Cancer Institute, University College London, London, WC1E 6DD, UK. c.armstrong@ucl.ac.uk.
authors.forename: Christine Anne
authors.initials: CA
authors.lastname: Armstrong
authors.affiliation: Chromosome Maintenance Group, UCL Cancer Institute, University College London, London, WC1E 6DD, UK. sian.pearson@ucl.ac.uk.
authors.forename: Siân Rosanna
authors.initials: SR
authors.lastname: Pearson
authors.affiliation: Chromosome Maintenance Group, UCL Cancer Institute, University College London, London, WC1E 6DD, UK. k.tomita@ucl.ac.uk.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Tomita
mesh_terms: D000595:Amino Acid Sequence; D015825:Chromosomes, Fungal / Q000378:metabolism*; D008540:Meiosis; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D060066:Protein Interaction Maps; D012568:Schizosaccharomyces / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000378:metabolism*; D000089804:Shelterin Complex; D016615:Telomere / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C510171:Bqt1 protein, S pombe; C510172:Bqt2 protein, S pombe; C509571:Rap1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins