What is the RISC complex and how does it relate to miRNA function?

RISC stands for RNA-Induced Silencing Complex. It is a multi-protein complex centered on an Argonaute (AGO) protein that uses a bound miRNA as a guide to find and silence complementary mRNA sequences. When a miRNA is loaded into RISC, the complex scans mRNAs for partial complementarity — unlike small interfering RNA (siRNA) which requires perfect complementarity, miRNA tolerates imperfect binding, allowing one miRNA to regulate hundreds of different target genes. When the RISC-miRNA complex finds a target mRNA, it either blocks ribosome translation or recruits RNA degradation machinery. In cancer, hyperactivated RISC-miRNA silencing of tumor suppressors is a key mechanism of malignant transformation. The mature miRNAs detected in urine by OncuraKit represent the loaded forms released from cells.