 The active components of an RNA @-@ induced silencing complex ( RISC ) are endonucleases called argonaute proteins , which cleave the target mRNA strand complementary to their bound siRNA . As the fragments produced by dicer are double @-@ stranded , they could each in theory produce a functional siRNA . However , only one of the two strands , which is known as the guide strand , binds the argonaute protein and directs gene silencing . The other anti @-@ guide strand or passenger strand is degraded during RISC activation . Although it was first believed that an ATP @-@ dependent helicase separated these two strands , the process proved to be ATP @-@ independent and performed directly by the protein components of RISC . However , an in vitro kinetic analysis of RNAi in the presence and absence of ATP showed that ATP may be required to unwind and remove the cleaved mRNA strand from the RISC complex after catalysis . The guide strand tends to be the one whose 5 ' end is less stably paired to its complement , but strand selection is unaffected by the direction in which dicer cleaves the dsRNA before RISC incorporation . Instead , the <unk> protein may serve as the differentiating factor by binding the more @-@ stable 5 ' end of the passenger strand . 
