Coupled protein quality control during nonsense-mediated mRNA decay

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Translation of messenger RNAs (mRNAs) with premature termination codons (PTCs) produces truncated proteins, which can be harmful.
• Nonsense-mediated decay (NMD) is a crucial cellular surveillance pathway that eliminates these PTC-containing mRNAs.
• The fate of the nascent truncated proteins generated from NMD targets has remained largely unknown.

Purpose of the Study:

• To investigate the degradation pathway of nascent proteins produced from NMD target mRNAs.
• To identify factors involved in the quality control of proteins linked to NMD.
• To determine if protein degradation relies on known pathways like the ribosome-quality control (RQC) pathway.

Main Methods:

• Utilized a fluorescent reporter system in mammalian cells to track protein products of NMD mRNAs.
• Employed genome-wide flow cytometry-based screens to identify factors involved in NMD-linked protein quality control.
• Conducted arrayed screens to compare mRNA and protein degradation pathways in NMD.

Main Results:

• Discovered a selective, post-translational degradation pathway for proteins arising from NMD mRNAs, dependent on the ubiquitin proteasome system.
• Genome-wide screens identified known NMD factors and indicated that protein degradation is independent of the canonical ribosome-quality control (RQC) pathway.
• Demonstrated that both the protein and mRNA branches of NMD share a common recognition event.

Conclusions:

• Established a targeted degradation pathway for nascent proteins from PTC-containing mRNAs.
• Provided a foundation for identifying and characterizing factors involved in NMD-linked protein quality control.
• Highlighted the coordinated action of mRNA and protein surveillance in cellular quality control mechanisms.