CFTR mRNAs with nonsense codons are degraded by the SMG6-mediated endonucleolytic decay pathway

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Approximately 10% of cystic fibrosis (CF) patients have CFTR gene nonsense mutations.
• Nonsense mutations lead to premature stop codons in CFTR mRNA, triggering nonsense-mediated decay (NMD) and rapid mRNA degradation.
• The specific NMD pathways regulating CFTR mRNA decay remain unclear.

Purpose of the Study:

• To investigate the NMD branches responsible for degrading CFTR mRNA containing nonsense codons.
• To assess the impact of NMD pathway inhibition on CFTR mRNA levels and translational readthrough therapy outcomes.

Main Methods:

• Utilized antisense oligonucleotides to target and inhibit specific NMD factors.
• Evaluated the requirement of UPF2, UPF3, SMG6, and SMG5-SMG7 pathways in CFTR mRNA decay.
• Assessed the efficacy of NMD inhibition in conjunction with translational readthrough therapy.

Main Results:

• CFTR mRNAs with G542X, R1162X, and W1282X nonsense codons require UPF2 and UPF3 for NMD.
• All evaluated nonsense codon-containing CFTR mRNAs are degraded via the SMG6-mediated endonucleolytic pathway, not SMG5-SMG7.
• Inhibiting the NMD pathway significantly upregulates nonsense codon-containing CFTR mRNAs.

Conclusions:

• Specific NMD factors (UPF2, UPF3) and the SMG6 pathway are crucial for CFTR nonsense mRNA decay.
• NMD pathway inhibition is a promising strategy to enhance CFTR mRNA levels.
• This approach improves the effectiveness of translational readthrough therapy for cystic fibrosis patients with nonsense mutations.