Vol. 12, Issue 1, 143-154, January 2001

Amino-terminal Polypeptides of Vimentin Are Responsible for the Changes in Nuclear Architecture Associated with Human Immunodeficiency Virus Type 1 Protease Activity in Tissue Culture Cells

Robert L. Shoeman,^* Claudia Hüttermann, Roland Hartig, and Peter Traub

Max-Planck-Institut für Zellbiologie, Rosenhof, D-68526 Ladenburg, Germany

Electron microscopy of human skin fibroblasts syringe-loaded with human immunodeficiency virus type 1 protease (HIV-1 PR) revealed several effects on nuclear architecture. The most dramatic is a change from a spherical nuclear morphology to one with multiple lobes or deep invaginations. The nuclear matrix collapses or remains only as a peripheral rudiment, with individual elements thicker than in control cells. Chromatin organization and distribution is also perturbed. Attempts to identify a major nuclear protein whose cleavage by the protease might be responsible for these alterations were unsuccessful. Similar changes were observed in SW 13 T3 M [vimentin⁺] cells, whereas no changes were observed in SW 13 [vimentin] cells after microinjection of protease. Treatment of SW 13 [vimentin] cells, preinjected with vimentin to establish an intermediate filament network, with HIV-1 PR resulted in alterations in chromatin staining and distribution, but not in nuclear shape. These same changes were produced in SW 13 [vimentin] cells after the injection of a mixture of vimentin peptides, produced by the cleavage of vimentin to completion by HIV-1 PR in vitro. Similar experiments with 16 purified peptides derived from wild-type or mutant vimentin proteins and five synthetic peptides demonstrated that exclusively N-terminal peptides were capable of altering chromatin distribution. Furthermore, two separate regions of the N-terminal head domain are primarily responsible for perturbing nuclear architecture. The ability of HIV-1 to affect nuclear organization via the liberation of vimentin peptides may play an important role in HIV-1-associated cytopathogenesis and carcinogenesis.