Final answer:
The RNA-induced silencing complex (RISC) is part of the RNA interference pathway where it, along with DICER, regulates gene expression by binding siRNAs or miRNAs to target and degrade complementary mRNA, leading to gene silencing.
Step-by-step explanation:
The RNA-induced silencing complex (RISC) is a critical component of the gene silencing pathway used by cells to regulate gene expression and defend against foreign RNA elements. When double-stranded RNA (dsRNA) from viruses or other sources enters a cell, it is recognized and cleaved by an enzyme called DICER into small interfering RNAs (siRNAs) or microRNAs (miRNAs). These fragments then engage with RISC, a ribonucleoprotein complex, which carries out the gene silencing process. siRNAs and miRNAs have slightly different mechanisms of action but both result in the downregulation of target RNA molecules.
The siRNA-RISC complex pairs with complementary mRNA, leading to its degradation, effectively silencing the gene. On the other hand, miRNAs in the miRNA-RISC complex can inhibit translation or lead to mRNA degradation depending on the degree of complementarity to their target sequence. This biological process, known as RNA interference (RNAi), is also being researched for its potential in treating viral infections by using designed siRNAs to target specific viral genes for silencing.