title: Hip3 interacts with the HIRA proteins Hip1 and Slm9 and is required for transcriptional silencing and accurate chromosome segregation.
abstract: The fission yeast HIRA proteins Hip1 and Slm9 are members of an evolutionarily conserved family of histone chaperones that are implicated in nucleosome assembly. Here we have used single-step affinity purification and mass spectrometry to identify factors that interact with both Hip1 and Slm9. This analysis identified Hip3, a previously uncharacterized 187-kDa protein, with similarity to S. cerevisiae Hir3. Consistent with this, cells disrupted for hip3+ exhibit a range of growth defects that are similar to those associated with loss of Hip1 and Slm9. These include temperature sensitivity, a cell cycle delay, and synthetic lethality with cdc25-22. Furthermore, genetic analysis also indicates that disruption of hip3+ is epistatic with mutation of hip1+ and slm9+. Mutation of hip3+ alleviates transcriptional silencing at several heterochromatic loci, including in the outer (otr) centromeric repeats, indicating that Hip3 is required for the integrity of pericentric heterochromatin. As a result, loss of Hip3 function leads to high levels of minichromosome loss and an increased frequency of lagging chromosomes during mitosis. Importantly, the function of Hip1, Slm9, and Hip3 is not restricted to constitutive heterochromatic loci, since these proteins also repress the expression of a number of genes, including the Tf2 retrotransposons.
authors.affiliation: Institute of Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom.
authors.forename: Amanda
authors.initials: A
authors.lastname: Greenall
authors.forename: Emma S
authors.initials: ES
authors.lastname: Williams
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Martin
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Palmer
authors.forename: Joe
authors.initials: J
authors.lastname: Gray
authors.forename: Cong
authors.initials: C
authors.lastname: Liu
authors.forename: Simon K
authors.initials: SK
authors.lastname: Whitehall
mesh_terms: D002846:Chromatography, Affinity; D020090:Chromosome Segregation; D015825:Chromosomes, Fungal; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D007211:Indoles; D013058:Mass Spectrometry; D008856:Microscopy, Fluorescence; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D012313:RNA / Q000032:analysis; D012568:Schizosaccharomyces / Q000235:genetics / Q000254:growth & development; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014158:Transcription, Genetic
chemical_list: D005456:Fluorescent Dyes; C562347:Hip3 protein, S pombe; D007211:Indoles; D018832:Molecular Chaperones; D029702:Schizosaccharomyces pombe Proteins; C007293:DAPI; D012313:RNA; D016650:Fluorescein-5-isothiocyanate