MULTIPLE INTERACTIONS CONTROL THE INTRACELLULAR-LOCALIZATION OF THE HERPES-SIMPLEX VIRUS TYPE-1 CAPSID PROTEINS

Herpes simplex virus type 1 (HSV-1) capsid assembly takes place in the nucleus of infected cells, However, when each of the outer capsid she ll proteins, VP5, VP23 and VP26, is expressed in the absence of any ot her HSV-1 proteins, it does not localize to the nucleus but is distrib uted throughout the cell, We have previously shown that the HSV-1 caps id scaffolding protein, preVP22a, can relocate VP5 into the nucleus bu t does not influence the distribution of VP23, We now demonstrate that the outer capsid shell protein, VP19C, is able to relocate both VP5 a nd VP23 separately into the nucleus, However, nuclear localization of VP26 is only observed when VP5 is present together with either VP1SC o r preVP22a, Thus, pair-wise interactions involving all of the abundant capsid proteins have now been identified. Electron microscope examina tion of insect cells coinfected with recombinant baculoviruses express ing VP1SC and VP5 reveals the presence of 70nm diameter 'capsid-like' structures, suggesting that these two proteins can form the basic caps id shell.