title: Yeast linker histone Hho1p is required for efficient RNA polymerase I processivity and transcriptional silencing at the ribosomal DNA.
abstract: Nucleosome core particles in eukaryotes are linked by a stretch of DNA that is usually associated with a linker histone. Here, we show in yeast, that the presence of yeast linker histone Hho1p represses expression of a pol II transcribed gene (MET15) embedded in the rDNA. In vivo deletions of Hho1p sequences showed that the second globular domain is sufficient for that repression, whereas the presence of the N terminus is required for its derepression. In contrast, a run-on assay confirmed by a ChIP experiment showed that Hho1p is required for maximal pol I processivity during rDNA transcription. Psoralen accessibility experiments indicated that Hho1p is necessary for normal rDNA compaction. DNA array expression analysis comparing RNA transcripts in wild-type and hho1 strains before and after a heat-shock showed that Hho1p is necessary to achieve wild-type mRNA levels of transcripts that encode ribosomal components. Taken together, our results suggest that Hho1p is involved in rDNA compaction, and like core histones, is required for efficient rDNA transcription by pol I.
authors.affiliation: The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan 52900, Israel.
authors.forename: Anat
authors.initials: A
authors.lastname: Levy
authors.forename: Miri
authors.initials: M
authors.lastname: Eyal
authors.forename: Gitit
authors.initials: G
authors.lastname: Hershkovits
authors.forename: Mali
authors.initials: M
authors.lastname: Salmon-Divon
authors.forename: Michael
authors.initials: M
authors.lastname: Klutstein
authors.forename: Don Jay
authors.initials: DJ
authors.lastname: Katcoff
mesh_terms: D003547:Cysteine Synthase; D004275:DNA, Ribosomal / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D012318:RNA Polymerase I / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; C480035:HHO1 protein, S cerevisiae; D006657:Histones; D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D003547:Cysteine Synthase; C103381:MET17 protein, S cerevisiae; D012319:RNA Polymerase II; D012318:RNA Polymerase I