title: Telomeric Retrotransposon HeT-A Contains a Bidirectional Promoter that Initiates Divergent Transcription of piRNA Precursors in Drosophila Germline.
abstract: PIWI-interacting RNAs (piRNAs) provide the silencing of transposable elements in the germline. Drosophila telomeres are maintained by transpositions of specialized telomeric retroelements. piRNAs generated from sense and antisense transcripts of telomeric elements provide telomere length control in the germline. Previously, we have found that antisense transcription of the major telomeric retroelement HeT-A is initiated upstream of the HeT-A sense transcription start site. Here, we performed a deletion analysis of the HeT-A promoter and show that common regulatory elements are shared by sense and antisense promoters of HeT-A. Therefore, the HeT-A promoter is a bidirectional promoter capable of processive sense and antisense transcription. Ovarian small RNA data show that a solo HeT-A promoter within an euchromatic transgene initiates the divergent transcription of transgenic reporter genes and subsequent processing of these transcripts into piRNAs. These events lead to the formation of a divergent unistrand piRNA cluster at solo HeT-A promoters, in contrast to endogenous telomeres that represent strong dual-strand piRNA clusters. Solo HeT-A promoters are not immunoprecipitated with heterochromatin protein 1 (HP1) homolog Rhino, a marker of the dual-strand piRNA clusters, but are associated with HP1 itself, which provides piRNA-mediated transcriptional repression of the reporter genes. Unlike endogenous dual-strand piRNA clusters, the solo HeT-A promoter does not produce overlapping transcripts. In a telomeric context, however, bidirectional promoters of tandem HeT-A repeats provide a read-through transcription of both genomic strands, followed by Rhi binding. These data indicate that Drosophila telomeres share properties of unistrand and dual-strand piRNA clusters.
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: Elizaveta
authors.initials: E
authors.lastname: Radion
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: Sergei
authors.initials: S
authors.lastname: Ryazansky
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: Natalia
authors.initials: N
authors.lastname: Akulenko
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: Yakov
authors.initials: Y
authors.lastname: Rozovsky
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Kwon
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: Valeriya
authors.initials: V
authors.lastname: Morgunova
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Olovnikov
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia. Electronic address: allakalm@img.ras.ru.
authors.forename: Alla
authors.initials: A
authors.lastname: Kalmykova
mesh_terms: D000818:Animals; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005854:Germ Cells; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012322:RNA Precursors / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics*; D018626:Retroelements / Q000235:genetics*; D016615:Telomere / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D029721:Drosophila Proteins; D012322:RNA Precursors; D034741:RNA, Small Interfering; D018626:Retroelements
keywords: Rhino; chromatin; divergent transcription; piRNA cluster; telomere