Final answer:
mRNA targeted by miRNA is typically degraded or has its translation inhibited, due to the binding of the miRNA to complementary sequences in the mRNA, a process essential to gene expression regulation and as a target for cancer therapeutics.
Step-by-step explanation:
The Fate of mRNA Targeted by miRNA
The ultimate fate of an mRNA that is targeted by a microRNA (miRNA) stands in the regulation of gene expression at the post-transcriptional level. When miRNAs bind to their complementary sequences on an mRNA molecule, they commonly lead to mRNA degradation or inhibition of its translation. miRNAs are part of a complex with proteins known as the RNA-induced silencing complex (RISC), which facilitates the reduction of mRNA stability and hence decreases protein synthesis. Certain miRNAs like miR-21, when overexpressed can cause malignant phenotypes, hence they are targets for the development of cancer therapeutics. The pathway involves miRNA binding to the target mRNA with partial or full complementarity, after which mRNA can be either cleaved and degraded if the pairing is complete or translation can be inhibited when the pairing is partial.