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Comments on Zinovyeva, Anna Y. et al. (2011) International Worm Meeting "Characterization of novel alleles of the C. elegans microRNA specific Argonaute ALG-1." (0)
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Zinovyeva, Anna Y., Hammell, Christopher C., & Ambros, Victor (2011). Characterization of novel alleles of the C. elegans microRNA specific Argonaute ALG-1 presented in International Worm Meeting. Unpublished information; cite only with author permission.
MicroRNAs (miRNAs) are small ~22nt molecules that function in many developmental processes by affecting target gene expression at the post-transcriptional level. ALG-1 is one of the two C. elegans argonautes important for miRNA biogenesis and function. We will report isolation of antimorphic (anti) alleles of ALG-1 that arose as suppressors of lin-28(lf) precocious developmental phenotypes. These alg-1 mutations result in single amino acid changes in the mid and PIWI domains of ALG-1. The mutant animals display dosage dependent phenotypes that are more severe than complete loss of ALG-1 function. The alg-1(anti) mutants each produce an apparently full-length ALG-1 protein that fails to interact with the miRISC (miRNA induced silencing complex) component AIN-1, but that retains interaction with Dicer and the miRISC component CGH-1. Interestingly, alg-1(anti) mutations do not result in the microRNA biogenesis defects seen in alg-1(null) animals, suggesting that miRNA processing remains mostly undisturbed in alg-1(anti) mutants. This conclusion is further supported by qRT/PCR (mirTaqman) quantitation of the levels of mature miRNAs in alg-1(anti) mutants, which are roughly equivalent to the levels in wild type animals. Deep sequencing analysis did not show a dramatic difference in the miRNA* populations between wild type and alg-1(anti) mutant animals, suggesting that the alg-1(anti) phenotypes are not caused by an inappropriate retention of the passenger (*) strand. We conclude that the alg-1(anti) mutations cause antimorphic phenotypes by producing an ALG-1 miRISC that lacks effector function (due to inability to interact with AIN-1), but that nevertheless loads with microRNAs, and thereby competes with ALG-2 for a limiting pool of microRNAs.
Affiliations:
- Molecular Medicine, University of Massachusetts Medical School, Worcester, MA.
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY