title: Ribosome biogenesis factors bind a nuclear envelope SUN domain protein to cluster yeast telomeres.
abstract: Two interacting ribosome biogenesis factors, Ebp2 and Rrs1, associate with Mps3, an essential inner nuclear membrane protein. Both are found in foci along the nuclear periphery, like Mps3, as well as in the nucleolus. Temperature-sensitive ebp2 and rrs1 mutations that compromise ribosome biogenesis displace the mutant proteins from the nuclear rim and lead to a distorted nuclear shape. Mps3 is known to contribute to the S-phase anchoring of telomeres through its interaction with the silent information regulator Sir4 and yKu. Intriguingly, we find that both Ebp2 and Rrs1 interact with the C-terminal domain of Sir4, and that conditional inactivation of either ebp2 or rrs1 interferes with both the clustering and silencing of yeast telomeres, while telomere tethering to the nuclear periphery remains intact. Importantly, expression of an Ebp2-Mps3 fusion protein in the ebp2 mutant suppresses the defect in telomere clustering, but not its defects in growth or ribosome biogenesis. Our results suggest that the ribosome biogenesis factors Ebp2 and Rrs1 cooperate with Mps3 to mediate telomere clustering, but not telomere tethering, by binding Sir4.
authors.affiliation: Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Horigome
authors.forename: Takafumi
authors.initials: T
authors.lastname: Okada
authors.forename: Kyoko
authors.initials: K
authors.lastname: Shimazu
authors.forename: Susan M
authors.initials: SM
authors.lastname: Gasser
authors.forename: Keiko
authors.initials: K
authors.lastname: Mizuta
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D004271:DNA, Fungal / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000378:metabolism; D016615:Telomere / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D004271:DNA, Fungal; C499008:EBP2 protein, S cerevisiae; D008565:Membrane Proteins; C471174:Mps3 protein, S cerevisiae; D009687:Nuclear Proteins; C485770:RRS1 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae