Structure, expression profile and alternative processing of the human phosphatidylethanolamine N-methyltransferase (PEMT) gene

Phosphatidylethanolamine N-methyltransferase (PEMT) catalyzes the conversio n of phosphatidylethanolamine (PE) to phosphatidylcholine (PC) in a series of three methylation reactions. Preliminary studies of PEMT in humans led t o the cloning of three cDNAs each of which has a different 5 ' untranslated region (5 ' UTR). To determine the origin of PEMT splice variants and to i nvestigate expression of the gene in human liver, we isolated a bacterial a rtificial chromosome (BAC) clone containing the full-length human gene. Eac h of the three unique untranslated first exons is present in a contiguous a rray in the gene, confirming the integrity of the cDNAs and alternative pro cessing of PEMT transcripts. Human liver, heart and testis contain the high est levels of PEMT transcripts and of these, liver has the greatest PEMT ex pression. Furthermore, each of the three PEMT transcripts is present in var ying abundance in liver whereas heart and testis contain only one and two t ranscripts, respectively. Thus, differential promoter usage in the human PE MT gene generates three unique transcripts and confers a tissue-specific ex pression pattern. (C) 2001 Elsevier Science B.V. All rights reserved.