title: Genetics of P-element transposition into Drosophila melanogaster centric heterochromatin.
abstract: Heterochromatin is a major component of higher eukaryotic genomes, but progress in understanding the molecular structure and composition of heterochromatin has lagged behind the production of relatively complete euchromatic genome sequences. The introduction of single-copy molecular-genetic entry points can greatly facilitate structure and sequence analysis of heterochromatic regions that are rich in repeated DNA. In this study, we report the isolation of 502 new P-element insertions into Drosophila melanogaster centric heterochromatin, generated in nine different genetic screens that relied on mosaic silencing (position-effect variegation, or PEV) of the yellow gene present in the transposon. The highest frequencies of recovery of variegating insertions were observed when centric insertions were used as the source for mobilization. We propose that the increased recovery of variegating insertions from heterochromatic starting sites may result from the physical proximity of different heterochromatic regions in germline nuclei or from the association of mobilizing elements with heterochromatin proteins. High frequencies of variegating insertions were also recovered when a potent suppressor of PEV (an extra Y chromosome) was present in both the mobilization and selection generations, presumably due to the effects of chromatin structure on P-element mobilization, insertion, and phenotypic selection. Finally, fewer variegating insertions were recovered after mobilization in females, in comparison to males, which may reflect differences in heterochromatin structure in the female and male germlines. FISH localization of a subset of the insertions confirmed that 98% of the variegating lines contain heterochromatic insertions and that these schemes produce a broader distribution of insertion sites. The results of these schemes have identified the most efficient methods for generating centric heterochromatin P insertions. In addition, the large collection of insertions produced by these screens provides molecular-genetic entry points for mapping, sequencing, and functional analysis of Drosophila heterochromatin.
authors.affiliation: Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, San Diego, CA 92037, USA.
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Konev
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Yan
authors.forename: David
authors.initials: D
authors.lastname: Acevedo
authors.forename: Cameron
authors.initials: C
authors.lastname: Kennedy
authors.forename: Elaina
authors.initials: E
authors.lastname: Ward
authors.forename: Arlene
authors.initials: A
authors.lastname: Lim
authors.forename: Sanjay
authors.initials: S
authors.lastname: Tickoo
authors.forename: Gary H
authors.initials: GH
authors.lastname: Karpen
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000235:genetics; D004251:DNA Transposable Elements; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D005260:Female; D005854:Germ Cells / Q000166:cytology; D006570:Heterochromatin / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D010641:Phenotype; D012641:Selection, Genetic
chemical_list: D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D006570:Heterochromatin; C050680:y protein, Drosophila