What is the function of the 5' cap added to mRNA?

What is the function of the 5' cap added to mRNA?

• A. Signals splicing
• B. Aids ribosome binding
• C. Causes degradation
• D. Export of mRNA from nucleus

Answer: (B)

The 5' cap’s key function is to enable ribosome binding and start translation. It’s a modified guanine nucleotide added to the very 5' end of the mRNA soon after transcription begins. This cap is specifically recognized by cap-binding proteins like eIF4E, which recruit the rest of the initiation machinery and the small ribosomal subunit to the mRNA. This direct interaction is what allows the ribosome to bind efficiently and begin translating the message. The cap also helps protect the mRNA from 5' exonucleases and supports export from the nucleus, but the most immediate and defining role is facilitating translation initiation. Splicing signals come from other sequence elements and splicing factors, and while the cap contributes to mRNA stability and export, it does not define degradation; it’s the protection against degradation and the initiation factors that together with export support make the cap essential, with ribosome binding being the primary, direct function.

The 5' cap’s key function is to enable ribosome binding and start translation. It’s a modified guanine nucleotide added to the very 5' end of the mRNA soon after transcription begins. This cap is specifically recognized by cap-binding proteins like eIF4E, which recruit the rest of the initiation machinery and the small ribosomal subunit to the mRNA. This direct interaction is what allows the ribosome to bind efficiently and begin translating the message. The cap also helps protect the mRNA from 5' exonucleases and supports export from the nucleus, but the most immediate and defining role is facilitating translation initiation. Splicing signals come from other sequence elements and splicing factors, and while the cap contributes to mRNA stability and export, it does not define degradation; it’s the protection against degradation and the initiation factors that together with export support make the cap essential, with ribosome binding being the primary, direct function.