Incomplete splicing of simian virus 40 large T antigen transcripts in a transformed mouse cell line

The SV40 large T antigen transcripts from an SV40-transformed mouse embryo fibroblast cell line (215) have been analyzed by Northern blots and by mapping and sequencing of the corresponding cDNAs. We have observed that T antigen mRNA is highly overexpressed in the 215 cells, and is mostly unspliced, but there are no sequence changes at the splice sites. However, normal amounts of wild-type T antigen are produced, suggesting that the splicing and translation of T antigen RNA is tightly controlled in these cells.