Targeting Argonaute to chromatin
In many eukaryotes, siRNAs bound to Argonaute proteins guide chromatin-modifying enzymes to complementary loci, resulting in transcriptional gene silencing. Multiple lines of evidence indicate that siRNAs base-pair with longer RNAs produced at target loci, but the possibility that siRNAs base-pair directly with DNA remains an attractive hypothesis. In a recent study, Shimada et al. (pp. 2571-2580) conducted experiments that address these alternative hypotheses, yielding additional evidence that fission yeast siRNA-Argonaute silencing complexes are recruited to target loci exclusively via interactions with nascent transcripts.
This work was supported by NHMRC [grant numbers 973302, 179805, 157125, 1002160, 1063907] and ARC [grant number 130101705]. Nicolas Cherbuin and Kaarin Anstey’s Research Fellowship are funded by ARC [grant number ::: 120100227] and NHMRC [grant number 1002560].