DPV pUL15 possesses a potential NLS, which is important for the location of the terminase complex and for viral proliferation and genome cleavage.

In herpesvirus, the terminase subunit pUL15 is involved in cleavage of the viral genome concatemers in the nucleus. Previous studies have shown that herpes simplex virus 1 (HSV-1) pUL15 can enter the nucleus without other viral proteins and help other terminase subunits enter the nucleus. However, this study revealed that duck plague virus (DPV) pUL15 cannot localize independently to the nucleus and can only be localized in the nucleus in the presence of pUL28 and pUL33. However, the data suggested the presence of a potential nuclear localization signal (NLS) in DPV pUL15, which is important for the localization of the terminase subunits. Subsequently, several single-point mutants were constructed to identify the vital amino acids within the NLS. The conserved amino acids K187, R188, and K190 are critical for the nuclear localization of pUL15, pUL28, and pUL33 but not for their interaction. Furthermore, corresponding recombinant viruses were constructed. The results revealed that the mutations rUL15K187Q, rUL15K188Q and rUL15K190Q had an obvious influence on concatemeric genome cleavage, but only K190Q significantly affected the production of progeny virions. These findings indicate that the NLS is important for the functions of DPV pUL15. Overall, a potential NLS and the key amino acids in DPV pUL15 were identified. Mutations in K187, K188 and K190 affected the cleavage of the concatemeric genome, but only mutations in K190 had an obvious effect on viral proliferation.