Simian virus 40 (SV40)-specific proteins associated with the nuclear matrix isolated from adenovirus type 2-SV40 hybrid virus-infected HeLa cells carry SV40 U-antigen determinants.

The distribution of simian virus 40 (SV40)-specific proteins in nuclear subfractions of pulse-chase-labeled HeLa cells infected with nondefective adenovirus type 2 (Ad2)-SV40 hybrid viruses was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The SV40-specific proteins of Ad2+ND1, Ad2+ND2, and Ad2+ND5 specifically associate with the nuclear matrix and are virtually absent from the high-salt nuclear extract. In Ad2+ND4-infected HeLa cells, the SV40-specific proteins with molecular weights of 64,000 (64K) and lower also specifically associate with the nuclear matrix. The SV40-specific 72K, 74K, and 95K proteins were found both in the nuclear matrix and in the high-salt nuclear extract. Analyses of the nuclear matrices isolated from hybrid virus-infected cells by immunofluorescence microscopy showed that SV40 U-antigen-positive sera from SV40 tumor-bearing hamsters react with SV40-specific proteins integrated into nuclear matrices of HeLa cells infected by Ad2+ND1, Ad2+ND2, and Ad2+ND4, but not with nuclear matrices of HeLa cells infected by Ad2+ND5. This suggests that SV40-specific proteins of Ad2+ND1, Ad2+ND2, and Ad2+ND4 integrated into the nuclear matrix carry SV40 U-antigen determinants. The apparent discrepancy in the subcellular localization of SV40-specific proteins in hybrid virus-infected cells when analyzed by biochemical cell fractionation procedures and when analyzed by immunofluorescence staining is discussed.