title: RAP-1 factor is necessary for DNA loop formation in vitro at the silent mating type locus HML.
abstract: DNA fragments containing the silencers that flank the mating type genes at HML alpha are shown to bind specifically to the nuclear scaffold of yeast. The scaffold proteins are solubilized with urea and then renatured to form a soluble extract which allows reconstitution of sequence-specific DNA loops. At the silent mating type locus HML alpha, loops are formed by either silencer-silencer (E-I) interaction or silencer-promoter interactions (E-P and I-P). The nuclear protein RAP-1 fractionates efficiently with the nuclear scaffold, and binds to the E, I, and promoter regions. Affinity purification of RAP-1 and oligonucleotide competition show that RAP-1 is necessary for reconstitution of loops in vitro. These results are consistent with a model in which silencers define a chromatin loop within which occur modifications that maintain the promoter in an inactive state.
authors.affiliation: Swiss Institute for Experimental Cancer Research (ISREC), Epalinges s/Lausanne.
authors.forename: J F
authors.initials: JF
authors.lastname: Hofmann
authors.forename: T
authors.initials: T
authors.lastname: Laroche
authors.forename: A H
authors.initials: AH
authors.lastname: Brand
authors.forename: S M
authors.initials: SM
authors.lastname: Gasser
mesh_terms: D002874:Chromosome Mapping; D004271:DNA, Fungal / Q000235:genetics* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000235:genetics* / Q000302:isolation & purification; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D000072235:Mating Factor; D008854:Microscopy, Electron; D009687:Nuclear Proteins / Q000235:genetics; D010455:Peptides / Q000235:genetics*; D010675:Pheromones / Q000235:genetics; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014157:Transcription Factors
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D009687:Nuclear Proteins; D010455:Peptides; D010675:Pheromones; D014157:Transcription Factors; D000072235:Mating Factor