Characterization of SV40 T antigen associated with the nuclear matrix

Simian virus 40 (SV40) T antigen associated with the nuclear matrix of SV40-infected TC7 cells has been characterized. Pulse-chase studies on the turnover of T antigen in the different subcellular fractions show that T antigen turns over most rapidly in its association with the purified SV40 nucleoprotein complexes (NPCs) and undergoes a slower rate of turnover in its association with the nuclear matrix. In contrast, turnover of SV40 T antigen in its association with the other subcellular fractions is not detected during the same period of time. Tryptic peptide maps establish that NPC-associated T antigen and nuclear matrix-associated T antigen are chemically related, in that they have two additional methionine-containing peptides that are not found in the majority of T antigen molecules. The association of T antigen with the nuclear matrix is independent of SV40 DNA replication since T antigen is still present in the nuclear matrix after a 1-hr shift-up of tsA58-infected cells to the nonpermissive temperature. In addition, T antigen is associated with the nuclear matrices of both C6 and Cos7 transformed cells, indicating that the association of T antigen with the nuclear matrix is independent of its ability to initiate and support SV40 DNA replication.