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Illustration of showing a nuclear pore complex (NPC, light blue and white, bottom) in a cell's nuclear envelope and three enzyme/microRNA (micro ribonucleic acid) complexes. Directly above the pore is a pre-miRNA (precursor microRNA, red) complexed with the exportin-5(blue)/RanGTP(light violet) transport protein. Exportin-5/RanGTP transports pre-miRNAs from the cell nucleus to the cytoplasm via the nuclear pore complex. At top centre is the dicer-2 enzyme (blue) bound to a pre-miRNA (red) and the cofactor TRBP (transactivation response element RNA-binding protein, violet). Dicer processes the pre-miRNA in the cytoplasm to produce double-stranded miRNA molecules. At top right is an argonaute protein bound to a guide strand (red) of miRNA. The argonaute protein will incorporate the guide strand into the RNA-induced silencing complex (RISC), a multiprotein complex that acts to inhibit the expression of specific genes by regulating the expression of messenger RNA (mRNA)