Final answer:
RNA is protected from RNases by the 5' cap, poly-A tail, coating in RNA-stabilizing proteins, and the binding of RNA-binding proteins. These mechanisms shield RNA from exonucleases and interference from miRNAs.
Step-by-step explanation:
RNA avoids being destroyed by RNases in two primary ways: through protective “caps” known as the 5' cap and the poly-A tail, and by coating in RNA-stabilizing proteins. The 5' cap is a methylated guanosine triphosphate (GTP) molecule that is placed backward at the 5' end of the mRNA to protect it from 5' exonucleases. The poly-A tail consists of a series of adenine nucleotides at the 3' end, which guards against 3' exonuclease degradation. In addition, RNA-stabilizing proteins coat the pre-mRNA to protect it while it is being processed and exported out of the nucleus.
RNA structures, such as intramolecular base pairing, form a three-dimensional shape that is essential for function and provides inherent stability against degradation. Moreover, RNA-binding proteins (RBPs) can bind to the RNA, preventing the binding of miRNA that otherwise leads to RNA degradation.