What does miRNA do to mRNA?

The miRNA pairs with the target mRNA, causing a decrease in its expression. The degree of matching between the miRNA and mRNA determines whether the mRNA will be cleaved and degraded or translation of proteins will be inhibited. In specific, MiRNAs typically bind to the 3' untranslated region (UTR) of target mRNAs. During mRNA degradation, the binding of the miRNA to the target mRNA leads to its degradation by cellular enzymes. The target mRNA is cleaved and degraded, preventing translation into protein. In contrast, during miRNA inhibition the binding of the miRNA to the mRNA prevents ribosomes from effectively translating the mRNA into protein, leading to translational repression.