miRNAs control target mRNAs by attaching to partially matching sequences, but some target RNAs can have the opposite effect. In TDMD (target-directed miRNA degradation), binding of miRNAs to RNAs with extensive complementarity leads to miRNA 3′-end tailing, trimming, and loss.
“This process functions in the test tube with fly lysates, but also in cells in which viral RNAs can direct host miRNAs for degradation”
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Grosshans Lab 