A stepwise pathway for biogenesis of 24-nt secondary siRNAs and spreading of DNA methylation
| Autor: | Tatsuo Kanno, Antonius J. M. Matzke, Ulf Naumann, Marjori Matzke, Etienne Bucher, Johannes van der Winden, Lucia Daxinger |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
0106 biological sciences
Ribonuclease III RNA-induced transcriptional silencing Trans-acting siRNA Arabidopsis Biology 01 natural sciences General Biochemistry Genetics and Molecular Biology Article 03 medical and health sciences Gene Silencing RNA Small Interfering Enhancer Molecular Biology RNA-Directed DNA Methylation Post-transcriptional regulation RNA polymerase IV 030304 developmental biology Genetics 0303 health sciences General Immunology and Microbiology Arabidopsis Proteins General Neuroscience DNA-Directed RNA Polymerases DNA Methylation RNA-Dependent RNA Polymerase RNA silencing DNA methylation 010606 plant biology & botany Protein Binding |
| Zdroj: | The EMBO journal. 28(1) |
| ISSN: | 1460-2075 |
| Popis: | We used a transgene system to study spreading of RNA-directed DNA methylation (RdDM) during transcriptional gene silencing in Arabidopsis thaliana. Forward and reverse genetics approaches using this system delineated a stepwise pathway for the biogenesis of secondary siRNAs and unidirectional spreading of methylation from an upstream enhancer element into downstream sequences. Trans-acting, hairpin-derived primary siRNAs induce primary RdDM, independently of an enhancer-associated ‘nascent' RNA, at the target enhancer region. Primary RdDM is a key step in the pathway because it attracts the secondary siRNA-generating machinery, including RNA polymerase IV, RNA-dependent RNA polymerase2 and Dicer-like3 (DCL3). These factors act in a turnover pathway involving a nascent RNA, which normally accumulates stably in non-silenced plants, to produce cis-acting secondary siRNAs that induce methylation in the downstream region. The identification of DCL3 in a forward genetic screen for silencing-defective mutants demonstrated a strict requirement for 24-nt siRNAs to direct methylation. A similar stepwise process for spreading of DNA methylation may occur in mammalian genomes, which are extensively transcribed in upstream regulatory regions. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Plný text