Final answer:
In the nucleus, pre-miRNAs are processed into mature miRNAs by the protein Dicer and then target specific mRNAs for degradation with the help of the RNA-induced silencing complex (RISC). This mechanism is part of the cellular defense against viral RNA.
Step-by-step explanation:
The NUCLEUS plays a critical role in the processing of microRNAs (miRNAs), which are small RNA molecules involved in gene regulation. In the NUCLEUS, longer pre-miRNAs are synthesized and then processed into mature miRNAs by a protein called Dicer. These mature miRNAs are then associated with a complex known as the RNA-induced silencing complex (RISC). The RISC complex, containing miRNAs, targets specific mRNAs for degradation, thus preventing the production of particular proteins. This regulatory mechanism also applies to foreign RNA, such as viral double-stranded RNA (dsRNA), which is recognized and cleaved by the enzyme DICER and then directed by RISC to degrade complementary viral mRNAs.