Molecular cloning of a gene for a member of carcinoembryonic antigen (CEA) gene family; signal peptide and N-terminal domain sequences of nonspecific crossreacting antigen (NCA).

A 2073-base pair DNA fragment containing a part of gene for a member of carcinoembryonic antigen (CEA) gene family, has been isolated from human DNA library after screening with 32P-labeled 53-mer oligodeoxyribonucleotide corresponding to N-terminal 18 amino acids of CEA gene family and cDNA encoding CEA (1,2). The fragment contains two exons; the one encodes the first 60% of signal peptide and the other the rest of it in addition to 107 amino acids which correspond to the N-terminal domain of CEA (1,2). Apparently, the second intron is inserted between the first and the second nucleotides of the codon for 108th amino acid. The presence of Ala instead of Val as the 21st amino acid of the N-terminal domain indicates that the exon encodes nonspecific crossreacting antigen (NCA).