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Nonstop Decay in C. elegans : Examination of a Possible Role for Small Noncoding RNAs
Author(s) -
Youngman Elaine M
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.757.21
Subject(s) - small nucleolar rna , rna , biology , non coding rna , microrna , dicer , genetics , long non coding rna , caenorhabditis elegans , small rna , rna interference , messenger rna , microbiology and biotechnology , gene
In C. eleg ans, small noncoding RNAs known as 22G RNAs are synthesized by RNA‐dependent RNA polymerases and target thousands of protein‐coding mRNAs, repetitive sequences, and cryptic transcripts throughout the genome. In some cases, 22G RNA synthesis appears to be triggered as a secondary event downstream of targeting by C. elegans piRNAs (known as 21U RNAs) in a pathway that defends against non‐self RNA species. (1, 2) However, the synthesis of the majority of 22G RNAs is unaffected by loss of 21U RNAs, and the triggers for biosynthesis of these 21U‐independent 22Gs remain elusive. Using a comparative genomic approach in geographically distributed wild isolates of C. elegans , we have identified a locus (F43E2.6) at which loss of the stop codon is correlated with increased production of 22G RNAs. The F43 mRNA has a short 3′UTR with no further in frame stop codons, raising the intriguing possibility that 22G RNAs could be involved in a nonstop decay pathway in C. elegans . F43 is also targeted by an unusual Dicer product; however this Dicer product does not appear to act as a primary siRNA to trigger F43 22G RNAs. First, the Dicer product is expressed equally in strains with large differences (more than 10 fold) in 22G RNA levels. Second, this product is expressed only during embryogenesis, whereas F43 22G RNAs are expressed most strongly in adults. We have demonstrated that the 22G RNA expression phenotype at the F43 locus is genetically linked to the locus itself, and are currently assaying worms carrying CRISPR‐edited F43 loci that bear or lack a stop codon to determine whether the loss of a stop codon is indeed causal for increased 22G RNA production. In addition, we are generating CRISPR‐mediated edits that create additional nonstop alleles to ask whether this phenomenon is general, and are integrating reporter constructs that will allow us to ask whether 22G RNAs play a functional role in the nonsense‐mediated and no‐go decay pathways.