title: Homology directed repair is unaffected by the absence of siRNAs in Drosophila melanogaster.
abstract: Small interfering RNAs (siRNAs) defend the organism against harmful transcripts from exogenous (e.g. viral) or endogenous (e.g. transposons) sources. Recent publications describe the production of siRNAs induced by DNA double-strand breaks (DSB) in Neurospora crassa, Arabidopsis thaliana, Drosophila melanogaster and human cells, which suggests a conserved function. A current hypothesis is that break-induced small RNAs ensure efficient homologous recombination (HR). However, biogenesis of siRNAs is often intertwined with other small RNA species, such as microRNAs (miRNAs), which complicates interpretation of experimental results. In Drosophila, siRNAs are produced by Dcr-2 while miRNAs are processed by Dcr-1. Thus, it is possible to probe siRNA function without miRNA deregulation. We therefore examined DNA double-strand break repair after perturbation of siRNA biogenesis in cultured Drosophila cells as well as mutant flies. Our assays comprised reporters for the single-strand annealing pathway, homologous recombination and sensitivity to the DSB-inducing drug camptothecin. We could not detect any repair defects caused by the lack of siRNAs derived from the broken DNA locus. Since production of these siRNAs depends on local transcription, they may thus participate in RNA metabolism-an established function of siRNAs-rather than DNA repair.
authors.affiliation: Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Straße 25, D-81377, München, Germany.
authors.forename: Ines
authors.initials: I
authors.lastname: Schmidts
authors.affiliation: Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Straße 25, D-81377, München, Germany.
authors.forename: Romy
authors.initials: R
authors.lastname: Böttcher
authors.affiliation: Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Straße 25, D-81377, München, Germany.
authors.forename: Milijana
authors.initials: M
authors.lastname: Mirkovic-Hösle
authors.affiliation: Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Straße 25, D-81377, München, Germany Foerstemann@genzentrum.lmu.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Förstemann
mesh_terms: D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology; D059006:Chromosomes, Insect / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000187:drug effects / Q000235:genetics*; D000072669:Gene Editing; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D009154:Mutation / Q000235:genetics; D034741:RNA, Small Interfering / Q000378:metabolism*; D059767:Recombinational DNA Repair / Q000187:drug effects; D015053:Zygote / Q000378:metabolism
chemical_list: D060565:Argonaute Proteins; D029721:Drosophila Proteins; D034741:RNA, Small Interfering; D002166:Camptothecin