Orchestrating ribosomal activity from inside: effects of the nascent chain on the peptidyltransferase centre

Ribosomal progression through the open reading frames within mRNAs is frequently considered as uneventful when compared with the highly regulated initiation step. However, both RNA and nascent peptide can interact with the ribosome to influence how translation proceeds and can modify gene expression in several ways. 2A peptides are a class of sequences that, as nascent chains, pause ribosomes and drive a translation-termination reaction on a sense (proline) codon, followed by continued downstream translation. In the present paper, what is known about the 2A reaction is discussed, and 2A is compared with other sequences that, as nascent peptides, pause or stall translation.