We have studied at the ultrastructural level the localization of PML protein in response to adenovirus infection in HeLa cells. In nuclei of noninfected cells or at the early stage of infection, PML accumulated at the border of nuclear bodies as previously described [Koken et al. (1994) EMBO J. 13, 1073-1083]. Interestingly, we demonstrate herein that PML is also a component of the interchromatin granule-associated zones, recently described structures containing U1 snRNP [Visa et al. (1993) Eur. J. Cell Biol. 60, 308-321], suggesting that PML protein might be involved in some steps of splicing events. However, as the infection progressed these two cellular PML-containing structures disappeared but significant amounts of PML accumulated within two virus-induced structures, essentially the clear amorphous inclusions, but also the protein crystals. Relocalization of this protein to virus-induced structures may reflect an inactivation of PML functions.