The goal of this work was to study the interaction of bovine papillomavirus type 1 (BPV-1) episomal DNA with the nuclear matrix (NM). Two cell lines, BPV-1.4R and BPV-1.4H, were generated by cotransfection of C127 cells with BamHI-linearized BPV-1 and T8-pMV7, a neomycin selection vector. Both transfectants were morphologically different from each other and from parental cells. Studies were conducted to determine if NM protein composition changed with transfection of BPV-1. 2-D IEF PAGE analysis revealed that maintenance and expression of BPV-l causes changes in the expression of a small subset of nuclear matrix proteins. Southern blot analysis indicated that both transfectants carry episomal copies of linear BPV-l. Bal 31 nuclease digestion and anchored-PCR experiments further demonstrated the existence of linear episomal BPV-1 molecules. No alteration of sequences was observed by sequencing in the 5$\prime$ end and 3$\prime$ end of linear episomes. Northern blot analysis indicated that linear extrachromosomal BPV-1 molecules are transcribed. Studies of viral DNA interactions with the nucleus suggested that linear BPV-1 DNA is not free to diffuse in the nucleus and is associated with the nuclear matrix. However, weak interactions of the viral genome with the nuclear matrix were detected rather than high affinity associations usually found for cellular genes
