Final answer:
miRNAs bound in a RISC complex target and regulate mRNA stability, either impeding translation or promoting degradation of RNA molecules. High complementarity between miRNAs and their targets leads to mRNA degradation, serving as a key post-transcriptional gene regulation mechanism.
Step-by-step explanation:
When miRNAs are bound in a RISC (RNA-induced silencing complex), they play a crucial role in the regulation of gene expression. These miRNAs, in association with RISC, target mRNAs that are old, no longer needed, or damaged during transcription to regulate or decrease RNA stability. The miRNA-RISC complex can impair translation, cleave completely complementary mRNA, degrade the target mRNA, or increase the degradation rate of the RNA molecule.
RNA interference (RNAi) is a natural process being explored by researchers as a treatment option for viral infections. The miRNA-RISC complex can either bind to the target mRNA and inhibit its translation or promote its degradation, particularly if the miRNA sequence exhibits high complementarity to its target. This is a form of post-transcriptional gene regulation and RNA molecule degradation which has significant implications for understanding cellular defense mechanisms and the development of therapeutic strategies.