BPS2026 – Dissecting the human cytomegalovirus UL38:UL29 interaction regulating host antiviral responses

Human cytomegalovirus (HCMV) is a highly prevalent pathogen, a leading viral cause of congenital birth defects, and pathogenic in immunocompromised individuals. Current antiviral compounds are effective, but issues of toxicity and emergence of resistance limit their use. During infection, HCMV overcomes host antiviral responses through numerous strategies including suppressing apoptosis, stimulating translation, and altering gene expression. Viral UL38 sits at the intersection of these mechanisms, interacting with both host and viral proteins. UL38 binds to TSC2, enhancing protein translation. UL38 also binds to the viral protein UL29 which stimulates viral gene expression. The UL38:UL29 interaction stabilizes transcriptionally inactive p53. It also associates with cNuRD which is involved in chromatin remodeling. The UL38:UL29 interaction is critical for efficient viral replication and serves as a plausible therapeutic target against infection. However, the molecular details underlying this interaction are unknown. The goal of this project is to define the interacting regions and structure of UL38:UL29 and test their importance for modulating the host antiviral response. We expressed and purified both viral proteins from bacteria to study the interaction. When co-expressed, both proteins co-purified indicating a direct interaction in the absence of host cellular proteins. Further, analysis of purified UL38 by gel filtration suggests the protein exists as either a multimer or exists in an extended conformation. In silico analysis using AlphaFold predicts an unstructured c-terminus for UL38 and potential binding interfaces between UL38:UL29 complex. We are using AlphaFold to additionally test mutations designed to disrupt their interaction and optimize constructs for structural studies. Our work demonstrates the feasibility of dissecting this complex interaction through a variety of biochemical and structural approaches. These studies provide a foundation for targeting the UL38:UL29 interaction as a potential antiviral strategy.