fig1

Figure 1. Schematic illustration of canonical and non-canonical miRNA biogenesis pathways and their mechanisms of action. In the canonical pathway, pri-miRNAs transcribed by RNA polymerase II undergo nuclear processing by the Drosha-DGCR8 complex into pre-miRNAs. Pre-miRNAs are exported to the cytoplasm via exportin-5 and further cleaved by Dicer to form mature miRNA duplexes. Mature miRNAs are incorporated into the RISC, guiding AGO proteins to their target mRNAs, leading to translational inhibition, mRNA degradation, or deadenylation. In contrast, the non-canonical pathway involves mirtrons - special intron-derived miRNAs - which bypass Drosha processing by utilizing host gene mRNA splicing machinery to generate pre-miRNAs directly. miRNA: MicroRNA; pri-miRNAs: primary miRNAs; DGCR8: DiGeorge syndrome critical region gene 8; pre-miRNAs: precursor miRNAs; RISC: RNA-induced silencing complex; AGO: Argonaute.