What does RISC do to the ribosome?

RISC, which stands for RNA-induced silencing complex, plays a crucial role in the post-transcriptional regulation of gene expression, particularly through its interaction with messenger RNA (mRNA). When RISC binds to mRNA, it typically functions to block translation. This is achieved through mechanisms such as the degradation of the mRNA or by hindering the translational machinery from associating with the mRNA.

When RISC binds to a complementary region of an mRNA molecule, it can facilitate the endonucleolytic cleavage of the mRNA, leading to its degradation. Additionally, RISC can also inhibit translation by preventing ribosomes from efficiently initiating or progressing through the translation process.

In contrast to enhancing translation or stimulating proteolysis, RISC's primary function is to silence gene expression at the level of translation, thereby leading to a decrease in protein production. This mechanism is essential for various biological processes, including the regulation of developmental genes and responses to viral infections.