Correct option is D
Ribosome-associated quality control (RQC) is a mechanism that ensures the proper functioning of translation and ensures that defective or damaged mRNA does not result in the synthesis of faulty proteins. During RQC, the following processes occur:
- mRNA degradation (1): Damaged or stalled mRNA is identified and degraded to prevent the synthesis of incomplete or harmful proteins.
- Nascent protein degradation (2): If translation stalls due to faulty mRNA, the nascent protein (partially synthesized protein) is also degraded to prevent the accumulation of incomplete proteins.
- Disengagement of ribosome from mRNA (3): In RQC, when translation stalls, the ribosome disengages from the damaged mRNA, often resulting in the recruitment of factors that promote mRNA degradation and protein quality control.
However, ribosome-mRNA monosome degradation (4) does not occur as part of ribosome-associated quality control. Instead, when translation stalls, ribosomes are typically dissociated from the mRNA in a process known as ribosome rescue or quality control, not degradation of the monosome complex. The degradation typically affects the mRNA or the nascent protein, but not the ribosome-mRNA monosome itself.
Information Booster:
- Ribosome-associated quality control ensures that any mRNA that is defective or not properly processed is either repaired or degraded before the translation process continues. This prevents the synthesis of incomplete, faulty, or toxic proteins that could potentially damage the cell.
- In the case of ribosome stalling, the mRNA-ribosome complex can be recognized by specific quality control factors like RQC factors or aberrant mRNA surveillance proteins, which direct the complex for degradation.
- Ribosome dissociation happens as part of the quality control process to free up resources and prevent translation of faulty mRNA. This often leads to the degradation of the mRNA and any associated nascent protein chains.
