What does phosphorylation of the RNA polymerase II tail promote?

What does phosphorylation of the RNA polymerase II tail promote?

• A. Recruitment of capping factors
• B. Recruitment of splicing factors
• C. Recruitment of TBP
• D. Recruitment of transcription machinery at the promoter region

Answer: (A)

Phosphorylation of the RNA polymerase II tail primarily promotes the recruitment of capping factors. The specific phosphorylation events that occur on the C-terminal domain (CTD) of RNA polymerase II are crucial for the transition from transcription initiation to elongation. When the tail of RNA polymerase II undergoes phosphorylation, it acts as a molecular signal that facilitates the binding of various proteins that are necessary for the processing of the emerging mRNA. One of the primary needs during transcription is to ensure that the mRNA is properly processed and modified as it is being synthesized. Capping factors, which add a 5’ cap to the nascent mRNA, are some of the proteins that recognize the phosphorylated CTD and are recruited to the site of transcription. This capping is essential for mRNA stability, protection from degradation, and is also important for subsequent steps like splicing and translation. Other options like splicing factors and TBP are indeed recruited during different stages of transcription or processing, but they are not the primary targets of the phosphorylation event on the RNA polymerase II tail in the context of immediate recruitment right after transcription initiation. The focus on capping factors underscores the importance of mRNA processing in the overall transcription cycle.

Phosphorylation of the RNA polymerase II tail primarily promotes the recruitment of capping factors. The specific phosphorylation events that occur on the C-terminal domain (CTD) of RNA polymerase II are crucial for the transition from transcription initiation to elongation.

When the tail of RNA polymerase II undergoes phosphorylation, it acts as a molecular signal that facilitates the binding of various proteins that are necessary for the processing of the emerging mRNA. One of the primary needs during transcription is to ensure that the mRNA is properly processed and modified as it is being synthesized. Capping factors, which add a 5’ cap to the nascent mRNA, are some of the proteins that recognize the phosphorylated CTD and are recruited to the site of transcription. This capping is essential for mRNA stability, protection from degradation, and is also important for subsequent steps like splicing and translation.

Other options like splicing factors and TBP are indeed recruited during different stages of transcription or processing, but they are not the primary targets of the phosphorylation event on the RNA polymerase II tail in the context of immediate recruitment right after transcription initiation. The focus on capping factors underscores the importance of mRNA processing in the overall transcription cycle.