The multi-KH domain protein of Saccharomyces cerevisiae Scp160p contributes to the regulation of telomeric silencing.
Multi-KH domain proteins are highly evolutionarily conserved proteins that associate to polyribosomes and participate in RNA metabolism. Recent evidence indicates that multi-KH domain proteins also contribute to the structural organization of heterochromatin both in mammals and Drosophila. Here, we show that the multi-KH domain protein of Saccharomyces cerevisiae, Scp160p, contributes to silencing at telomeres and at the mating-type locus, but not to ribosomal silencing. The contribution of Scp160p to silencing is independent of its binding to the ribosome as deletion of the last two KH domains, which mediate ribosomal binding, has no effect on silencing. Disruption of SCP160 increases cell ploidy but this effect is also independent of the contribution of Scp160p to telomeric silencing as strong relief of silencing is observed in Deltascp160 cells with normal ploidy and, vice versa, Deltascp160 cells with highly increased ploidy show no significant silencing defects. The TPE phenotype of Deltascp160 cells associates to a decreased Sir3p deposition at telomeres and, in good agreement, silencing is rescued by SIR3 overexpression and in a Deltarif1Deltarif2 mutant. Scp160p shows a distinct perinuclear localization that is independent of its ability to bind ribosomes. Moreover, telomere clustering at the nuclear envelope is perturbed in Deltascp160 cells and disruption of the histone deacetylase RPD3, which is known to improve telomere clustering, rescues telomeric silencing in Deltascp160 cells. These results are discussed in the context of a model in which Scp160p contributes to silencing by helping telomere clustering.
Marsellach
Francesc-Xavier
FX
Departament de Biologia Molecular i Cellular, Institut de Biologia Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain.
Huertas
Dori
D
Azorín
Fernando
F
D002467:Cell Nucleus / Q000502:physiology; D020090:Chromosome Segregation; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins; D012270:Ribosomes / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D016615:Telomere / Q000502:physiology*
D008565:Membrane Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; C097262:SCP160 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins