HP1 recruitment in the absence of argonaute proteins in Drosophila

• Published in: PLoS genetics Vol. 6; no. 3; p. e1000880
• Main Authors: Moshkovich, Nellie, Lei, Elissa P
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.03.2010; Public Library of Science (PLoS)
• Subjects: Animals; Argonaute Proteins; Binding sites; Biochemistry/Transcription and Translation; Cell Biology/Gene Expression; Chromatin; Chromatin - metabolism; Chromosomal Proteins, Non-Histone - metabolism; Computational Biology/Transcriptional Regulation; Deoxyribonucleic acid; Developmental Biology/Developmental Molecular Mechanisms; DNA; DNA methylation; DNA Transposable Elements - genetics; Drosophila; Drosophila melanogaster - cytology; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Drosophila Proteins - metabolism; Eukaryotic Initiation Factors - metabolism; Female; Gene Expression Regulation; Gene Silencing; Genes; Genetic aspects; Genetic engineering; Genetic transcription; Genetics and Genomics/Epigenetics; Genetics and Genomics/Gene Expression; Genomes; Molecular Biology/Chromatin Structure; Molecular Biology/RNA-Protein Interactions; Mutagenesis, Insertional - genetics; Mutation; Mutation - genetics; Ovarian Follicle - cytology; Ovarian Follicle - metabolism; Physiological aspects; Properties; Protein Transport; Proteins; Recruitment; RNA, Small Interfering - metabolism; RNA-Induced Silencing Complex - metabolism; Standard deviation; Telomerase; Transcription, Genetic; Transposons; United States
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1000880

Highly repetitive and transposable element rich regions of the genome must be stabilized by the presence of heterochromatin. A direct role for RNA interference in the establishment of heterochromatin has been demonstrated in fission yeast. In metazoans, which possess multiple RNA-silencing pathways that are both functionally distinct and spatially restricted, whether RNA silencing contributes directly to heterochromatin formation is not clear. Previous studies in Drosophila melanogaster have suggested the involvement of both the AGO2-dependent endogenous small interfering RNA (endo-siRNA) as well as Piwi-interacting RNA (piRNA) silencing pathways. In order to determine if these Argonaute genes are required for heterochromatin formation, we utilized transcriptional reporters and chromatin immunoprecipitation of the critical factor Heterochromatin Protein 1 (HP1) to monitor the heterochromatic state of piRNA clusters, which generate both endo-siRNAs and the bulk of piRNAs. Surprisingly, we find that mutation of AGO2 or piwi increases silencing at piRNA clusters corresponding to an increase of HP1 association. Furthermore, loss of piRNA production from a single piRNA cluster results in genome-wide redistribution of HP1 and reduction of silencing at a distant heterochromatic site, suggesting indirect effects on HP1 recruitment. Taken together, these results indicate that heterochromatin forms independently of endo-siRNA and piRNA pathways.