TRIM28 facilitates type I interferon activation by targeting TBK1

Area of Science:

• Immunology
• Molecular Biology
• Virology

Background:

• Type I interferons are crucial for innate immunity against viruses, inducing antiviral genes to inhibit replication.
• Interferon activation relies on IRF3 transcription factor, phosphorylated by TBK1 kinase during viral infections.
• The precise mechanisms of TBK1 activation for IRF3 signaling are not fully understood.

Purpose of the Study:

• To identify novel regulators of type I interferon activation.
• To elucidate the role of tripartite motif containing 28 (TRIM28) in antiviral signaling.
• To understand how TRIM28 facilitates TBK1 activation and subsequent antiviral responses.

Main Methods:

• CRISPR-Cas9 gene editing to create TRIM28 knockout cells.
• Viral challenge assays using RNA and DNA viruses.
• Co-immunoprecipitation to study protein interactions (TRIM28 and TBK1).
• Analysis of post-translational modifications (K63-linked ubiquitination) and protein phosphorylation (TBK1, IRF3).

Main Results:

• Genetic deletion of TRIM28 impaired type I interferon activation against both RNA and DNA viruses.
• TRIM28 knockout cells showed increased susceptibility to viral infections.
• TRIM28 directly interacted with TBK1 and mediated K63-linked ubiquitination of TBK1.
• TRIM28 deficiency led to defective TBK1 phosphorylation, reduced TBK1-IRF3 complex formation, and impaired IRF3 phosphorylation.

Conclusions:

• TRIM28 acts as a positive regulator of type I interferon activation by facilitating TBK1 signaling.
• TRIM28 is a novel substrate for E3 ubiquitin ligase activity, promoting antiviral immunity.
• TRIM28 is essential for controlling innate antiviral immune responses through the TBK1-IRF3 pathway.