A gene amplified in a transformed mouse cell line undergoes complex transcriptional processing and encodes a nuclear protein.

We have explored the structure and pattern of expression of a gene designated mdm-1, which is amplified 25-30-fold in transformed mouse cells containing numerous double minute particles. This gene is expressed in all mouse tissues examined but exhibits elevated and altered patterns of expression in the testis. Multiple transcripts are generated from the mdm-1 gene via mechanisms of alternative splicing and polyadenylation signal choice. These mRNAs have the potential to produce a minimum of three distinct protein products ranging in size from 25 to 77 kilodaltons. Antiserum generated against a synthetic peptide from the mdm-1 gene was used in immunoblotting studies and revealed that at least one of the protein products is present in the nucleus. This antiserum stained nuclear structures producing a distinct punctate or speckled pattern.