Induction of a subnuclear structure by the simultaneous expression of baculovirus proteins, IE1, LEF3, and P143 in the presence of hr.

Baculoviruses elicit the formation of a nuclear domain, called the virogenic stroma, in which viral DNA replication and nucleocapsid assembly occur. We had previously reported that nuclear focus formation of a transcriptional activator, IE1, is triggered by its binding to a viral DNA element, hr, and predicted that this hr-induced IE1 focus is an initial scaffold for the virogenic stroma. However, LEF3, a component of the virogenic stroma, did not localize to the IE1 foci. In exploring a mediator for its localization, we found that a baculovirus DNA helicase (P143), in combination with IE1 and hr, induced a subnuclear structure to which LEF3 localized and also that another component of the virogenic stroma, DBP, is able to localize to this structure. These results reveal that only four viral molecules are necessary to establish a nuclear domain which possesses a recruiting ability for a component of the virogenic stroma.