By a differential screening procedure, we have obtained several cDNAs the expression of which was down-regulated in v-src-transformed 3Y1 cells compared to parental 3Y1 cells. One of these cDNAs, termed N26, was extensively analyzed. Sequence analysis revealed that N26 cDNA was 3,095 nucleotides in length and contained an open reading frame of 665 amino acid residues. Based on an homology search at the nucleotide level, it was postulated that N26 gene encodes lamin A. The expression of the N26 gene was not suppressed in other types of transformed cells, such as v-mos-, v-ras- and SV40-transformed 3Y1 cells.