Small interfering RNA (siRNA) biogenesis

Small interfering RNAs (siRNAs) are 21-25 nucleotide single-stranded RNAs produced by cleavage of longer double-stranded RNAs by the enzyme DICER1 within the RISC loading complex containing DICER1, an Argonaute protein, and either TARBP2 or PRKRA (PACT). Typically the long double-stranded substrates originate from viruses or repetitive elements in the genome and the two strands of the substrate are exactly complementary.<br>After cleavage by DICER1 the 21-25 nucleotide double-stranded product is loaded into an Argonuate protein (humans contain 4 Argonautes) and rendered single-stranded by a mechanism that is not well characterized.<br>siRNA-loaded AGO2 is predominantly located at the cytosolic face of the rough endoplasmic reticulum and has also been observed in the nucleus.

小干扰RNA（siRNA）是由DICER1酶在含有DICER1、Argonaute蛋白以及TARBP2或PRKRA（PACT）的RISC加载复合物中，通过切割较长的双链RNA而产生的21-25个核苷酸的单链RNA。通常，这些较长的双链底物源自病毒或基因组中的重复元件，且底物的两条链完全互补。<br>DICER1切割后，21-25个核苷酸的双链产物被装载入Argonaute蛋白（人类含有4种Argonaute蛋白）中，并通过一种尚不明确的机制转变为单链。<br>装载siRNA的AGO2主要位于粗糙内质网的细胞质面，并在核中也有观察到。