CHARACTERIZATION OF THE MURINE PHOSPHATIDYLETHANOL AMINE N-METHYLTRANSFERASE-2 GENE

Phosphatidylethanolamine N-methyltransferase (PEMT) catalyzes the conv ersion of phosphatidylethanolamine to phosphatidylcholine in the mamma lian liver via three sequential methylations. In the present studies, we cloned and characterized the murine gene for PEMT2, the isoform of the enzyme that localizes to the mitochondria-associated membrane. The structure of the gene was determined by analysis of two lambda and th ree P1 genomic clones, and compared to the known rat PEMT2 cDNA sequen ce. Southern blotting of mouse genomic DNA indicated that PEMT2 is a s ingle-copy gene. The gene spans at least 35 kb, with seven exons and s ix introns. Two transcription start sites, 139 and 148 base pairs upst ream of the translation start site, were detected by primer extension and reverse transcriptase-polymerase chain reaction. These experiments indicated that the PEMT2 gene is transcribed from a single promoter. Finally, the PEMT2 gene was localized to mouse chromosome 11 by inters pecific backcrossing. These experiments represent the first cloning an d characterization of a full-length mammalian gene involved in phospho lipid biosynthesis.