Physical and functional interactions between the herpes simplex virus UL15and UL28 DNA cleavage and packaging proteins

Herpes simplex virus (HSV) DNA is cleaved from concatemers and packaged int o capsids in infected cell nuclei. This process requires seven viral protei ns, including UL15 and UL28. UL15 expressed alone displays a nuclear locali zation, while UL28 remains cytoplasmic. Coexpression with UL15 enables UL28 to enter nuclei, suggesting an interaction between the two proteins. Addit ionally, UL28 copurified with UL15 from HSV-infected cells after ion-exchan ge and DNA affinity chromatography, and the complex sedimented as a 1:1 het erodimer upon sucrose gradient centrifugation. These findings are evidence of a physical interaction of UL15 and UL28 and a functional role for UL15 i n directing UL28 to the nucleus.