title: Two portable recombination enhancers direct donor choice in fission yeast heterochromatin.
abstract: Mating-type switching in fission yeast results from gene conversions of the active mat1 locus by heterochromatic donors. mat1 is preferentially converted by mat2-P in M cells and by mat3-M in P cells. Here, we report that donor choice is governed by two portable recombination enhancers capable of promoting use of their adjacent cassette even when they are transposed to an ectopic location within the mat2-mat3 heterochromatic domain. Cells whose silent cassettes are swapped to mat2-M mat3-P switch mating-type poorly due to a defect in directionality but cells whose recombination enhancers were transposed together with the cassette contents switched like wild type. Trans-acting mutations that impair directionality affected the wild-type and swapped cassettes in identical ways when the recombination enhancers were transposed together with their cognate cassette, showing essential regulatory steps occur through the recombination enhancers. Our observations lead to a model where heterochromatin biases competitions between the two recombination enhancers to achieve directionality.
authors.affiliation: Department of Biology, University of Copenhagen, BioCenter, Copenhagen, Denmark.
authors.forename: Tadas
authors.initials: T
authors.lastname: Jakočiūnas
authors.forename: Lærke Rebekka
authors.initials: LR
authors.lastname: Holm
authors.forename: Janne
authors.initials: J
authors.lastname: Verhein-Hansen
authors.forename: Ala
authors.initials: A
authors.lastname: Trusina
authors.forename: Geneviève
authors.initials: G
authors.lastname: Thon
mesh_terms: D004742:Enhancer Elements, Genetic; D005785:Gene Conversion; D049770:Genes, Mating Type, Fungal / Q000235:genetics*; D006570:Heterochromatin / Q000235:genetics*; D006801:Humans; D011995:Recombination, Genetic; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics
chemical_list: D006570:Heterochromatin