Secondary siRNAs Result from Unprimed RNA Synthesis and Form a Distinct Class

@article{Sijen2007SecondarySR,
  title={Secondary siRNAs Result from Unprimed RNA Synthesis and Form a Distinct Class},
  author={Titia Sijen and Florian A. Steiner and Karen L. Thijssen and Ronald H. A. Plasterk},
  journal={Science},
  year={2007},
  volume={315},
  pages={244 - 247}
}
In Caenorhabditis elegans, an effective RNA interference (RNAi) response requires the production of secondary short interfering RNAs (siRNAs) by RNA-directed RNA polymerases (RdRPs). We cloned secondary siRNAs from transgenic C. elegans lines expressing a single 22-nucleotide primary siRNA. Several secondary siRNAs start a few nucleotides downstream of the primary siRNA, indicating that non–RISC (RNA-induced silencing complex)–cleaved mRNAs are substrates for secondary siRNA production. In… Expand
Endogenous siRNAs from naturally formed dsRNAs regulate transcripts in mouse oocytes
TLDR
The results reveal a role for endogenous siRNAs in mammalian oocytes and show that organisms lacking RdRP activity can produce functional endogenous si RNAs from naturally occurring dsRNAs. Expand
New insights into siRNA amplification and RNAi
In the nematode Caenorhabditis elegans (C. elegans), gene inactivation by RNA interference can achieve remarkable potency due to the amplification of initial silencing triggers by RNA-dependent RNAExpand
Distinct phases of siRNA synthesis in an endogenous RNAi pathway in C. elegans soma.
TLDR
The requirement for two RdRP/Argonaute combinations and initiation by a rare class of uniquely structured siRNAs in this pathway illustrate the caution and flexibility used as biological systems exploit the physiological copying of RNA. Expand
In vitro analyses of the production and activity of secondary small interfering RNAs in C. elegans
TLDR
Primary rather than primary siRNAs may play a major role in the destabilization of target transcripts during RNAi in Caenorhabditis elegans. Expand
Identification of an RNA-dependent RNA polymerase in Drosophila establishes a common theme in RNA silencing
TLDR
The largest subunit of the Drosophila RNA polymerase II core elongator complex, called D-elp1, has RdRP activity capable of using unprimed or primed synthesis mechanisms to convert single stranded RNA templates into double stranded RNA (dsRNA) that can be cleaved by Dcr-2. Expand
MicroRNA–Directed siRNA Biogenesis in Caenorhabditis elegans
TLDR
It is shown that RDE-1 functions as a scavenger protein, taking up small RNA molecules from many different sources, including the microRNA (miRNA) pathway, in striking contrast to Argonaute proteins functioning directly in the miRNA pathway, ALG-1 and AlG-2: these proteins exclusively bind miRNAs. Expand
A Ribonuclease Coordinates siRNA Amplification and mRNA Cleavage during RNAi
TLDR
Together, the findings suggest a model in which RDE-8 cleaves target mRNAs to mediate silencing, while generating 3' uridylated mRNA fragments to serve as templates for the RdRP-directed amplification of the silencing signal. Expand
Endogenous Small RNAs in the Drosophila Soma: A Dissertation
TLDR
It is discovered, that irrespective of its biogenesis, a miRNA duplex can load into either Argonaute (Ago1 or Ago2), contingent on its structural and sequence features, followed by assignment of one of the strands in the duplex as the functional or guide strand. Expand
Role of RNA Interference (RNAi) in the Moss Physcomitrella patens
TLDR
The current knowledge on the role of RNAi in P. patens is summarized that shows functional overlap with RNAi pathways from seed plants, and also unique features specific to this species. Expand
Roles of Cellular RNA-Dependent RNA Polymerases in Endogenous Small RNA Pathways in Caenorhabditis elegans: A Dissertation
TLDR
This thesis describes genetic, deep sequencing, and molecular studies, which identify 22G-RNAs as the most abundant class of endogenous small RNA in C. elegans and shows that 22G -RNAs are dependent on and interact with members of an expanded family of worm-specific Argonaute proteins that interact with RdRPdependent small RNAs. Expand
...
1
2
3
4
5
...

References

SHOWING 1-10 OF 23 REFERENCES
On the Role of RNA Amplification in dsRNA-Triggered Gene Silencing
TLDR
Analysis of small interfering RNAs produced during RNAi in C. elegans revealed a substantial fraction that cannot derive directly from input dsRNA, and appeared to derive from the action of a cellular RNA-directed RNA polymerase (RdRP) on mRNAs that are being targeted by the RNAi mechanism. Expand
Evidence implying only unprimed RdRP activity during transitive gene silencing in plants
TLDR
It is shown that replicating plant viruses trigger an RNA silencing defence response that degrades the viral RNA, thus tempering the virus infection, and that transitive silencing in plants occurs by un-primed cRNA synthesis from the 3′ end of targeted (transgene) transcripts, and not by siRNAs serving as primers for c RNA synthesis by RNA-dependent RNA polymerase. Expand
RNA Helicase MUT-14-Dependent Gene Silencing Triggered in C. elegans by Short Antisense RNAs
TLDR
It is shown that single-stranded RNA oligomers of antisense polarity can also be potent inducers of gene silencing, and the data favor the hypothesis that genesilencing is accomplished by RNA primer extension using the mRNA as template, leading to dsRNA that is subsequently degraded. Expand
A microRNA in a Multiple-Turnover RNAi Enzyme Complex
TLDR
It is shown that, in human cell extracts, the miRNA let-7 naturally enters the RNAi pathway, which suggests that only the degree of complementarity between a miRNA and its RNA target determines its function. Expand
A Distinct Small RNA Pathway Silences Selfish Genetic Elements in the Germline
TLDR
The data suggest that rasiRNAs protect the fly germline through a silencing mechanism distinct from both the miRNA and RNA interference pathways. Expand
microRNA-Directed Phasing during Trans-Acting siRNA Biogenesis in Plants
TLDR
Data support a model in which miRNA-guided formation of a 5' or 3' terminus within pre-ta-siRNA transcripts, followed by RDR6-dependent formation of dsRNA and Dicer-like processing, yields phased ta-siRNAs that negatively regulate other genes. Expand
The dsRNA Binding Protein RDE-4 Interacts with RDE-1, DCR-1, and a DExH-Box Helicase to Direct RNAi in C. elegans
TLDR
This work shows that the C. elegans RNAi pathway gene, rde-4, encodes a dsRNA binding protein that interacts during RNAi with RNA identical to the trigger dsRNAs, and suggests a model in which RDE-4 and Rde-1 function together to detect and retain foreign ds RNA and to present this ds RNAs to DCR-1 for processing. Expand
The rde-1 Gene, RNA Interference, and Transposon Silencing in C. elegans
TLDR
It is shown that rde-1 is a member of the piwi/sting/argonaute/zwille/eIF2C gene family conserved from plants to vertebrates and the possibility that one natural function of RNAi is transposon silencing is discussed. Expand
A micrococcal nuclease homologue in RNAi effector complexes
TLDR
Tudor-SN is the first RISC subunit to be identified that contains a recognizable nuclease domain, and could therefore contribute to the RNA degradation observed in RNAi. Expand
Gene silencing in Caenorhabditis elegans by transitive RNA interference.
TLDR
Evidence that dsRNA is amplified in Caenorhabditis elegans to ensure a robust RNAi response is provided, and data suggest ds RNA synthesized in vivo can mediate systemic RNAi. Expand
...
1
2
3
...