The ERI-6/7 Helicase Acts at the First Stage of an siRNA Amplification Pathway That Targets Recent Gene Duplications

• DOI: 10.1371/journal.pgen.1002369
• Publication Date: 2011-11-10T21:55:26Z
• Authors: Sylvia E. J. Fischer; Taiowa A. Montgomery; Chi Zhang; Noah Fahlgren; Peter C. Breen; Alexia Hwang; Christopher M. Su...; James C. Carrington; Gary Ruvkun
• Keywords: Dicer; Trans-acting siRNA; Argonaute; RNA Helicase A

Endogenous small interfering RNAs (siRNAs) are a class of naturally occuring regulatory found in fungi, plants, and animals. Some endogenous siRNAs required to silence transposons or function chromosome segregation; however, the specific roles most unclear. The helicase gene eri-6/7 was identified nematode Caenorhabditis elegans by enhanced response exogenous double-stranded (dsRNAs) null mutant. encodes homologous RNA factors Armitage Drosophila, SDE3 Arabidopsis, Mov10 humans. Here we show that mutations cause loss 26-nucleotide (nt) derived from genes pseudogenes oocytes embryos, as well deficiencies somatic 22-nucleotide secondary corresponding same loci. About 80 targets generate embryonic mRNAs. These share extensive nucleotide sequence homology poorly conserved, suggesting role for these silencing thereby directing fate recently acquired, duplicated genes. Unlike C. elegans, eri-6/7–dependent require Dicer. We identify have passenger strand is ∼19 nt inset ∼3–4 nts both ends 26 guide siRNA, non-canonical Dicer processing. Mutations Argonaute ERGO-1, which associates with siRNAs, stabilization, indicating ERGO-1 separate siRNA duplex, presumably through endonucleolytic cleavage strand. Thus, like several other siRNA–associated Argonautes conserved RNaseH motif, appears be maturation.