Which process is not considered part of post-transcriptional processing?

Post-transcriptional processing refers to the modifications that pre-mRNA undergoes after transcription but before it is translated into a protein. Among the modifications involved in this process are 5' capping, splicing, and 3' polyadenylation.

5' capping is vital as it involves adding a modified guanine nucleotide to the 5' end of the mRNA, which protects the mRNA from degradation and assists in ribosome binding during translation.

Splicing is an essential step that removes introns (non-coding sequences) from the pre-mRNA and joins exons (coding sequences) together, leading to a mature mRNA strand that can be translated into a protein.

3' polyadenylation adds a string of adenine nucleotides to the 3' end of the mRNA, which also helps stabilize the mRNA and facilitates its export from the nucleus.

On the other hand, polypeptide splicing is not part of post-transcriptional processing. Instead, it refers to the process that occurs during translation, where the protein is synthesized and the polypeptide chains fold and may undergo further modifications after their synthesis. Therefore, noting that polypeptide splicing occurs after transcription and translation –