Final answer:
Nonsense-Mediated Decay (NMD) is an mRNA surveillance system that degrades mRNAs with premature stop codons to prevent the production of malfunctioning proteins. It involves several steps, including ribosome stalling, UPF protein interactions, phosphorylation, and dephosphorylation events, ultimately leading to mRNA decapping and degradation. The correct option is B.
Step-by-step explanation:
The process described in the question points to an mRNA surveillance mechanism known as Nonsense-Mediated Decay (NMD), which is a quality control system that degrades mRNAs containing premature stop codons, thus preventing the synthesis of truncated and potentially harmful proteins.
The detailed sequence of NMD involves the ribosome stalling at a premature termination codon (PTC), interaction with exon-junction complexes (EJCs) downstream of the stop codon through UPF proteins, and phosphorylation of UPF1 which is crucial for NMD activation.
Following this, the ribosome dissociates due to phosphorylation, and later, UPF1 is dephosphorylated by a complex consisting of SMG6, SMG5/7, and PP2A, signaling the mRNA for decapping, and hence promoting its decay.
NMD is a sophisticated biological process that includes various factors like translation termination, interaction with mRNA modifications such as the 5' cap, and roles of different release factors and enzymes. It ensures the precision of gene expression and prevents the accumulation of faulty proteins that can be deleterious to the cell.