How Human Cytomegalovirus UL3 Can Serve as a Drug Target Based on Its Structure and Function

HCMV is a β-herpesvirus found in humans that can cause systemic infection; both an acute infection and a later latency and periodic reactivation event can cause disease in immunocompromised patients. Therefore, pinpointing genes involved in infection can potentially be used to design inhibitors against the virus. The purpose of this research project is to examine UL3, a viral gene with unknown structure and function. Within this study, I wanted to discover when UL3 was expressed during the viral life cycle and if it is required for viral growth. First, I cloned UL3 into the plasmid vector, pSNAPf, using designed primers and molecular biology techniques. This will allow us to see where in the cell the UL3 protein is localized by detecting the SNAP tag. To study UL3 within the virus, I used a virus (HCMV-UL3-HA) where UL3 is tagged with a different epitope tag, HA. To ensure the HA tag was not inhibiting the natural function and growth of the virus, I performed a virus titer using HCMV UL3-HA virus compared to wild type HCMV in fibroblasts (NHDFs). I also looked at structure predictions of UL3 using Alphafold to compare it to other known proteins, and sequence similarity tools such as BLAST to compare UL3 to known sequences. Future directions for this project include creating a growth curve for a knock-out HCMV UL3 virus against the HCMV UL3-HA virus to see if UL3 is required for viral growth. We can also use the HCMV UL3-HA virus to determine when UL3 is expressed by quantifying the HA protein tag attached to UL3 using a western blot. Once we know this information, we can potentially target the UL3 gene with a drug to take out the virus during acute infection.