Representative examples of newly identified miRNA regulatory mechanisms. (A) Pri-miRNA genes frequently utilize multiple alternative promoters, as exemplified by the transcript that encodes let-7a-3 and let-7b. The RefSeq noncoding transcript MIRLET7BHG is shown in blue. (B) Pri-miRNAs may host subsets of clustered miRNAs, as illustrated by transcripts that encode miR-100, let-7a-2, and miR-125b-1. The RefSeq noncoding transcript MIR100HG is shown in blue. (C) miRNAs may span splice sites and thereby may be regulated by alternative splicing. The pri-miRNA that encodes miR-205 is shown as a representative example of this configuration. The RefSeq noncoding transcript MIR205HG is shown in blue.
