EXAMINATION OF DETERMINANTS FOR INTRANUCLEAR LOCALIZATION AND TRANSACTIVATION WITHIN THE RING FINGER OF HERPES-SIMPLEX VIRUS TYPE-1 IE1 1OKPROTEIN

The herpesvirus regulatory protein IE110k possesses a cysteine-rich, R ING finger motif required for its role in transactivation and virus re plication, IE110k also localizes to subnuclear compartments termed POD s (PML oncogenic domains), Localization to PODs induces redistribution of the proteins associated with this nuclear compartment, including t he cellular RING finger protein, PML, Here we construct a series of de letions, RING domain swaps and point mutations to analyse specific req uirements within the IE110k RING finger for subnuclear localization, r edistribution of PML and transactivation and we examine the relationsh ip between these activities, We find that IE110k localizes to distinct nuclear subdomains that are more numerous than the cellular PODs and that mutation of two residues within a predicted loop of the RING fing er, or replacing the IE110k RING finger with a RING finger from a cell ular gene abrogates the ability of IE110k to localize to these extra c ompartments and traps IE110k in the original PODs. We further demonstr ate that RING fingers from the cellular genes mdm-2 and Bmi I, when pl aced within IE110k, alter the nuclear distribution of IE110k, do not t ransactivate, and do not redistribute PML, We also demonstrate that th e majority of wild-type IE110k, like PML, is associated with the nucle ar matrix, Although substitutions and deletions within the RING finger abolish transactivation, these mutant proteins remain tightly associa ted with the matrix, These results further dissect the determinants in volved in different aspects of nuclear compartmentalization of IE110k and are discussed in relation to PML, PODs and the IE110k RING finger.