Which component is crucial for ensuring that mRNA is stable in the cytoplasm?

The 5' cap is a crucial modification added to the nascent mRNA during transcription that significantly contributes to the stability of mRNA in the cytoplasm. This modified guanine nucleotide protects the RNA from degradation by exonucleases, which are enzymes that degrade RNA molecules. The 5' cap also plays a vital role in the initiation of translation by facilitating the binding of the ribosome to the mRNA. Additionally, it contributes to the transport of mRNA from the nucleus to the cytoplasm.

Without the 5' cap, mRNA would be more susceptible to rapid degradation, leading to reduced protein synthesis and overall decreased expression of the genes encoded by that mRNA. This protective mechanism is essential for maintaining the integrity and functionality of the mRNA during its lifecycle in the cytoplasm.

Other components mentioned, such as transcription factors and RNA polymerase, are more directly related to the initiation and regulation of transcription in the nucleus, while ribosomes are essential for translating mRNA into proteins but do not play a significant role in mRNA stability per se.