# Duck Plague Virus Full-Length UL15 Protein Is a Multifunctional Enzyme Which Not Only Possesses Nuclease Activity but Also Exerts ATPase and DNA-Binding Activity

## TL;DR

This study shows that the DPV pUL15 protein has three key functions: DNA binding, ATP hydrolysis, and DNA cleavage, making it essential for viral DNA packaging.

## Contribution

The study identifies the full-length DPV pUL15 as a multifunctional enzyme with independent ATPase, DNA-binding, and nuclease activities.

## Key findings

- Full-length pUL15 exhibits non-sequence-specific nuclease activity.
- The N-terminal region of pUL15 is responsible for DNA-binding and ATPase functions.
- The C-terminal region of pUL15 is responsible for nuclease activity, independent of the other functions.

## Abstract

Duck plague virus (DPV), an alphaherpesvirus, utilizes a terminase complex for genome packaging. This study focuses on the large terminase subunit, pUL15, and characterizes its functional domains. The results showed that the full-length pUL15 protein exhibits three key enzymatic activities: it binds and cleaves DNA non-specifically, and hydrolyzes ATP. Further analysis using truncated mutants mapped the DNA-binding and ATPase functions to the N-terminal region, whereas the nuclease activity was localized to the C-terminus. Notably, these functions are independent, as the loss of nuclease activity did not impair the other two. These findings confirm DPV pUL15 as a multifunctional enzyme essential for genome processing and provide a fundamental basis for understanding the mechanism of viral DNA packaging in herpesviruses.

The genome of the herpesvirus is a linear double-stranded DNA. The viral genome replicates in the host cell to form a concatemeric DNA, which is then cleaved to produce a unit-length genome. This unit-length genome is packaged into procapsid to produce mature virus particles. The terminase large subunit, pUL15, mediates the cleavage and packaging of viral concatemeric genomes. Duck plague virus (DPV) is a member of the α herpesvirus subfamily. Previous studies have demonstrated that the C-terminal region of DPV pUL15 exhibits non-sequence-specific DNA cleavage activity in vitro, but the characteristics of DPV full-length pUL15 remain unclear. In this study, it was determined that the full-length pUL15 exerted non-sequence-specific nuclease activity. Additionally, full-length pUL15 was capable of binding to DNA and hydrolyzing ATP. To analyze the functional domain of DPV pUL15, pUL15 mutants were constructed, expressed, and purified. The results revealed that DNA-binding and ATPase functions of pUL15 were primarily mediated by its N-terminal region, and the nuclease activity was conducted by its C-terminus. The loss of the nuclease activity did not effect on the DNA-binding and ATPase activity. Taken together, this study’s findings demonstrated that DPV pUL15 is a multifunctional enzyme with ATPase, nuclease, and DNA-binding activities. These results will provide important clues for subsequent studies on the function of terminase and the process of viral genome packaging, and provide a foundational basis for the development of broad-spectrum anti-herpesviral drugs targeting the conserved terminase complex, with direct relevance to veterinary medicine.