TY - JOUR T1 - Key role of piRNAs in telomeric chromatin maintenance and telomere nuclear positioning in <em>Drosophila</em> germline JF - bioRxiv DO - 10.1101/163030 SP - 163030 AU - Elizaveta Radion AU - Valeriya Morgunova AU - Sergei Ryazansky AU - Natalia Akulenko AU - Sergey Lavrov AU - Yuri Abramov AU - Ivan Olovnikov AU - Alla Kalmykova Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/07/13/163030.abstract N2 - Background Telomeric small RNAs related to PIWI-interacting RNAs (piRNAs) were discovered in different eukaryotes, however, their role in germline-specific telomere function remains poorly understood. Using a Drosophila model, we performed an in-depth study of the biogenesis of telomeric piRNAs and their function in telomere homeostasis in the germline.Results Telomeric transgenes were used to monitor the piRNA production and chromatin structure of particular telomeric loci. Small RNA-seq data has shown that telomeric arrays belong to a class of dual-strand piRNA clusters, but the ability to produce piRNAs varies along telomeric transposon arrays. Rhino, a germline-specific homolog of heterochromatic protein 1 (HP1), associates with all telomeric transgenes and its level correlates with the abundance of transgenic piRNAs. In contrast to conventional dual-strand piRNA clusters, piRNA loss causes sharp decrease of HP1, Rhino and trimethylated histone H3 lysine 9 levels at telomeric regions, Thus, the presence of piRNAs are required for telomere chromatin maintenance in the germline. Moreover, piRNA loss causes telomere translocation from the nuclear periphery towards the nuclear interior but does not affect telomere end capping or clustering. Chromatin analysis of telomere-associated sequences (TAS) revealed strong tissue specificity of silencing mechanisms exerted by subtelomeric regions.Conclusions piRNAs provide a germline-specific mechanism of telomeric chromatin assembly. Telomeric arrays belong to a unique type of self-targeting dual-strand piRNA clusters whose transcripts serve as piRNA precursors and their only targets at the same time. Telomeric chromatin is highly sensitive to piRNA loss suggesting a primary role of Drosophila telomeres in the response to the disruption of genome integrity. ER -