RNA-induced silencing complex (RISC), molecular model. This complex consists of a bacterial argonaute protein (top right) bound to a small interfering RNA (siRNA) molecule (red and blue). RISC is the multiprotein complex responsible for the gene silencing process known as RNA interference (RNAi). This involves one strand of siRNA, used as a template for recognising complementary mRNA (messenger RNA), and an argonaute protein that catalyses the RNA interference process. This complex plays a role in gene regulation and defence against viral infection.