Trans-acting Si RNA - Biosynthesis

Biosynthesis

Ta-siRNAs are generated from non coding transcripts through Argonaute mediated miRNA guided cleavage followed by conversion to double stranded RNA by the RNA-dependent RNA polymerase RDR6 and suppressor of gene silencing 3 (SGS3). The resulting dsRNA is further processed by dicer-like enzyme 4 (DCL4) to produce a phased array of 21-nt siRNAs. starting at the miRNA cleavage site.

There are four families of ta-siRNAs. The families get their names from the location in TAS gene from where they are transcribed. TAS1, TAS2, and TAS4 families require one mRNA binding site for cleavage to occur while TAS3 requires two binding sites.