title: Topological constraints on transvection between white genes within the transposing element TE35B in Drosophila melanogaster.
abstract: The transposable element TE35B carries two copies of the white (w) gene at 35B1.2 on the second chromosome. These w genes are suppressed in zeste-1 (z1) mutant background in a synapsis-dependent manner. Single-copy derivatives of the original TE35B stock give red eyes when heterozygous, but zeste eyes when homozygous. TE35B derivatives carrying single, double or triple copies of w were crossed to generate flies carrying from two to five ectopic w genes. Within this range, z1-mediated suppression is insensitive to copynumber and does not distinguish between w genes that are in cis or in trans. Suppression does not require the juxtaposition of even numbers of w genes, but is extremely sensitive to chromosomal topology. When arranged in a tight cluster, in triple-copy TE derivatives, w genes are nonsuppressible. Breakpoints falling within TE35B and separating two functional w genes act as partial suppressors of z1. Similarly, breakpoints immediately proximal or distal to both w genes give partial suppression. This transvection-dependent downregulation of w genes may result from mis-activation of the X-chromosome dosage compensation mechanism.
authors.affiliation: Department of Genetics, University of Cambridge, United Kingdom. d.gubb@gen.cam.ac.uk
authors.forename: D
authors.initials: D
authors.lastname: Gubb
authors.forename: J
authors.initials: J
authors.lastname: Roote
authors.forename: J
authors.initials: J
authors.lastname: Trenear
authors.forename: D
authors.initials: D
authors.lastname: Coulson
authors.forename: M
authors.initials: M
authors.lastname: Ashburner
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000818:Animals; D002869:Chromosome Aberrations; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D005136:Eye Proteins; D005260:Female; D017344:Genes, Insect; D019476:Insect Proteins / Q000235:genetics*; D008297:Male; D009154:Mutation; D009690:Nucleic Acid Conformation; D010641:Phenotype; D010860:Pigments, Biological; D014162:Transfection
chemical_list: D018528:ATP-Binding Cassette Transporters; D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D005136:Eye Proteins; D019476:Insect Proteins; D010860:Pigments, Biological; C059254:w protein, Drosophila