SUZ domain-containing proteins have multiple effects on nonsense-mediated decay target transcripts

Area of Science:

• Molecular Biology
• Gene Regulation
• RNA Metabolism

Background:

• Nonsense-mediated decay (NMD) is a surveillance pathway that degrades specific mRNA transcripts and inhibits their translation.
• SUZ domain-containing proteins are involved in various cellular processes, but their role in NMD has not been fully elucidated.

Purpose of the Study:

• To investigate the interaction of SZRD1 with NMD factors and its role in regulating protein production from NMD-targeted transcripts.
• To determine if other SUZ domain-containing proteins share similar functions in NMD regulation.

Main Methods:

• Co-immunoprecipitation to assess protein interactions.
• Reporter gene assays to measure protein production from NMD-sensitive transcripts.
• Western blotting to analyze protein and NMD factor levels after SZRD1 knockdown.

Main Results:

• SZRD1 interacts with UPF1, a key NMD factor, and enhances protein production from NMD-sensitive transcripts by relieving translational inhibition.
• The SUZ domain of SZRD1 is crucial for this function.
• ARPP21, another SUZ domain-containing protein, also enhances protein production from NMD-sensitive transcripts in an SUZ domain-dependent manner.
• SZRD1 knockdown reduces UPF3B levels and increases a subset of NMD targets, suggesting a role beyond translational inhibition relief.

Conclusions:

• Human SUZ domain-containing proteins, including SZRD1 and ARPP21, can prevent translational inhibition of NMD targets.
• SZRD1 plays a complex role in NMD regulation, influencing both translational inhibition and the levels of NMD factors like UPF3B.