Impaired K48-polyubiquitination downmodulates mouse norovirus propagation.

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Noroviruses are highly contagious RNA viruses causing widespread gastroenteritis.
• Lack of effective therapies necessitates understanding norovirus pathogenesis.
• Ubiquitination is a key post-translational modification regulating cellular processes.

Purpose of the Study:

• To investigate the role of ubiquitination in regulating anti-noroviral responses.
• To determine how specific ubiquitination chain linkages affect norovirus replication.

Main Methods:

• Generated RAW264.7 cells overexpressing wild-type (WT) or mutant YFP-Ubiquitin (K29R, K48R, K63R).
• Infected cells with murine norovirus S99 strain (MNoV_S99).
• Assessed viral marker expression, viral genome copies, and viral titers.

Main Results:

• Cells expressing YFP-Ubiquitin_K48R showed significantly impaired expression of viral markers (NS5, NS7, VP1, dsRNA).
• Viral genome copies and titers were significantly decreased in YFP-Ubiquitin_K48R cells.
• This effect was linked to constitutive TNF hypersecretion, IκBα phosphorylation, and NF-κB nuclear translocation, not altered viral entry.

Conclusions:

• K48-linked ubiquitination negatively regulates MNoV_S99 replication.
• This regulation creates a non-permissive cellular environment for norovirus.
• Findings reveal a novel host-intrinsic antiviral mechanism involving ubiquitination.