Final answer:
During elongation, the carboxyl terminal domain (CTD) of eukaryotic RNA polymerase undergoes phosphorylation, which recruits factors involved in mRNA processing and termination. These modifications are essential for proper transcription.
Step-by-step explanation:
During the elongation phase of eukaryotic RNA polymerase, the carboxyl terminal domain (CTD) undergoes several important modifications. The CTD consists of multiple repeats of the heptapeptide sequence Tyr-Ser-Pro-Thr-Ser-Pro-Ser and plays a critical role in transcription by recruiting and coordinating various factors involved in mRNA processing and transcription termination.
When RNA polymerase enters the elongation phase, the CTD becomes phosphorylated at specific serine residues. This phosphorylation triggers the recruitment of mRNA capping enzymes, splicing factors, and the machinery involved in 3' end processing of the mRNA. Additionally, the phosphorylated CTD aids in the recruitment of transcription termination factors, ensuring proper termination of transcription.
Overall, the modifications of the carboxyl terminal domain of eukaryotic RNA polymerase during the elongation phase are crucial for proper mRNA processing and termination of transcription.