RESUMO
In Drosophila, 23-30 nt long PIWI-interacting RNAs (piRNAs) direct the protein Piwi to silence germline transposon transcription. Most germline piRNAs derive from dual-strand piRNA clusters, heterochromatic transposon graveyards that are transcribed from both genomic strands. These piRNA sources are marked by the heterochromatin protein 1 homolog Rhino (Rhi), which facilitates their promoter-independent transcription, suppresses splicing, and inhibits transcriptional termination. Here, we report that the protein Maelstrom (Mael) represses canonical, promoter-dependent transcription in dual-strand clusters, allowing Rhi to initiate piRNA precursor transcription. Mael also represses promoter-dependent transcription at sites outside clusters. At some loci, Mael repression requires the piRNA pathway, while at others, piRNAs play no role. We propose that by repressing canonical transcription of individual transposon mRNAs, Mael helps Rhi drive non-canonical transcription of piRNA precursors without generating mRNAs encoding transposon proteins.
Assuntos
Elementos de DNA Transponíveis , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimologia , RNA Polimerase II/metabolismo , RNA Guia de Cinetoplastídeos/biossíntese , RNA Mensageiro/biossíntese , RNA Interferente Pequeno/biossíntese , Transcrição Gênica , Animais , Proteínas Argonautas/genética , Proteínas Argonautas/metabolismo , Sítios de Ligação , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Regulação da Expressão Gênica , Regiões Promotoras Genéticas , Ligação Proteica , RNA Helicases/genética , RNA Helicases/metabolismo , RNA Polimerase II/genética , RNA Guia de Cinetoplastídeos/genética , RNA Mensageiro/genética , RNA Interferente Pequeno/genéticaRESUMO
Severe congenital neutropenia is an inherited bone marrow failure disorder characterized by profoundly low neutrophil counts and promyelocytic maturation arrest in bone marrow. Severe congenital neutropenia is most often caused by heterozygous ELANE mutations. In vitro and mouse xenograft studies using CRISPR/Cas9 have shown that introduction of frameshift/nonsense mutations in mutant ELANE may restore neutrophil counts, providing a model for gene therapy. Here, we present 2 children with inherited nonsense mutations in ELANE analogous to those proposed for gene therapy. Their normal peripheral blood neutrophil counts provide support for this approach through human "experiments of nature."