Answer :
Final answer:
The fate of mRNA upon miRNA binding is determined by the extent of complementary base pairing, particularly involving the miRNA's seed region, and the involvement of Argonaute in the RNA-induced silencing complex.
Explanation:
The destruction of target mRNA by microRNAs (miRNAs) is a sophisticated mechanism of post-transcriptional gene regulation. When miRNAs bind to their target mRNAs, they typically do so through a "seed" region, which is a short stretch at the 5' end of the miRNA that is critical for recognition. If the seed region of a miRNA forms complementary base pairing with an mRNA, the complex is usually recognized by the Argonaute protein, which is a part of the RNA-induced silencing complex (RISC).
Depending on the degree of complementarity between the miRNA and the mRNA, different outcomes can occur:
- If there is nearly perfect complementarity beyond the seed region, the Argonaute protein can directly cleave the mRNA, leading to its degradation.
- If the complementarity is less extensive, typically involving just the seed region, the miRNA-mRNA complex can still lead to repression of translation, and sometimes deadenylation and subsequent decay of the mRNA.
So, while both the extent of miRNA binding and the involvement of Argonaute can influence mRNA fate, it is not accurate to say that miRNA or Argonaute cuts the mRNA in all instances. Rather, the degree of base pairing and interaction with RISC components ultimately determines mRNA stability and translational efficiency.
