Alternate miRNA sources and noncanonical targeting. A schematic depicting the varying sources identified for production of mature miRNAs, including the 5′ or 3′ strand of the traditional miRNA hairpin structure, processing of other noncoding RNAs, such as lncRNAs, small nucleolar RNAs (snoRNAs), miRNAs transcribed from the same gene but having different mature miRNA sequences (isomiRs), and miRNA spliced from introns (miRtrons). Nontraditional miRNA targets beyond the 3′ UTR are also depicted, including promoter regions of protein-coding genes, the 5′ UTR, the RNA coding sequence, and protein.