Identification of the membrane association of BV/ODV E26 and the domains in BV/ODV E26 responsible for nuclear trafficking to intranuclear microvesicles

The baculovirus Autographa californica nucleopolyhedrovirus (AcNPV) has two viral forms, budded virus (BV) and occlusion derived virus (ODV). The envelopment of these two viral forms occurs at different locations: BV acquires envelopes at the plasma membrane while ODV acquires envelopes in the nucleus. The two viral forms carry out different functions in the viral life cycle. The purpose of this study is to investigate how viral envelope proteins sort/traffic to the nucleus. Of particular interest is BV/ODV E26 (E26). E26 is an envelope protein of both BV and ODV (Braunagel and Summers, 1994); therefore it must traffic to the plasma membrane and the nucleus during infection. Thus, E26 is a bi-directional trafficking protein, which interacts with membranes in both locations of the cell. As such it has been shown that there are several immunoreactive forms of E26 (Beniya, Braunagel, and Summers, 1998). The da26 gene produces at least 2 protein products of 26 and 28 kDa with different functions respectively, which correlate with localization, solubility, membrane association, and temporal requirements. The 28 kDa form is likely a soluble protein that interacts with transcriptional activators and DNA in the nucleus in the early stages of infection. A part of the 26 kDa population is a membrane bound form interacting with an integral membrane protein in the ER and likely functions as an INM sorting factor. The 26 kDa membrane bond form is also found in the inner nuclear membrane, intra-nuclear microvesicles, ODV envelopes, and ODV in the nucleus