title: Mutations in Su(var)205 and Su(var)3-7 suppress P-element-dependent silencing in Drosophila melanogaster.
abstract: In Drosophila melanogaster, the w(+) transgene in P[lacW]ci(Dplac) is uniformly expressed throughout the adult eye. However, when other P elements are present, this w(+) transgene is randomly silenced and this produces a variegated eye phenotype. This P-element-dependent silencing (PDS) is limited to w(+) transgenes inserted in a specific region on chromosome 4. In a screen for genetic modifiers of PDS, we isolated mutations in Su(var)205, Su(var)3-7, and two unidentified genes that suppress this variegated phenotype. Therefore, only a few of the genes encoding heterochromatic modifiers act dose dependently in PDS. In addition, we recovered two spontaneous mutations of P[lacW]ci(Dplac) that variegate in the absence of P elements. These P[lacW]i(Dplac) derivatives have a gypsy element inserted proximally to the P[lacW]ci(Dplac) insert. The same mutations that suppress PDS also suppress w(+) silencing from these P[lacW]ci(Dplac) derivative alleles. This indicates that both cis-acting changes in sequence and trans-acting P elements cause a similar change in chromatin structure that silences w(+) expression in P[lacW]ci(Dplac). Together, these results confirm that PDS occurs at P[lacW]ci(Dplac) because of the chromatin structure at this chromosomal position. Studying w(+) variegation from P[lacW]ci(Dplac) provides a model for the interactions that can enhance heterochromatic silencing at single P-element inserts.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bushey
authors.forename: John
authors.initials: J
authors.lastname: Locke
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism; D005123:Eye / Q000378:metabolism; D018628:Gene Dosage; D005786:Gene Expression Regulation / Q000502:physiology*; D020868:Gene Silencing; D005799:Genes, Dominant; D006570:Heterochromatin / Q000235:genetics; D010858:Pigmentation / Q000235:genetics
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D006570:Heterochromatin; C000716867:Su(var)205 protein, Drosophila; C449619:Su(var)3-7 protein, Drosophila; D000090266:Chromobox Protein Homolog 5