Nuclear localization of human immunodeficiency virus type 1 integrase expressed as a fusion protein with green fluorescent protein

Lentiviruses in general and the human immunodeficiency virus type 1 (HIV-1) in particular have the ability to integrate their genome stably into the c hromosome of nondividing cells. Integration of HIV cDNA is mediated by the viral integrase (IN). Apart from its catalytic activity, this enzyme seems to play an important role in the transport of the HIV preintegration comple x into the nucleus of nondividing cells. We studied the karyophilic propert ies of IN by constructing an N-terminal fusion protein of HIV-1 integrase a nd green fluorescent protein (GFP-IN). Transient expression of GFP-IN in va rious mammalian cell lines was demonstrated by fluorescence microscopy, flo w cytometry, and Western blotting. Although wild-type GFP was localized thr oughout the cell, GFP-IN was localized predominantly in the nucleus. Nuclea r localization of GFP-IN was also obtained after transient transfection of the cells arrested in the G(1)/S phase of the cell cycle. These results pro vide compelling evidence for the karyophilic properties of the HIV-1 integr ase. (C) 1999 Academic Press.