title: Regulatory effects of genomic translocations at the human carboxylesterase-1 (CES1) gene locus.
abstract: OBJECTIVE
  CES1 encodes carboxylesterase-1, an important drug-metabolizing enzyme with high expression in the liver. Previous studies have reported a genomic translocation of the 5' region from the poorly expressed pseudogene CES1P1, to CES1, yielding the structural variant CES1VAR. The aim of this study was to characterize this translocation and its effect on CES1 expression in the human liver.
  
  
  METHODS
  Experiments were conducted in human liver tissues and cell culture (HepG2). The promoter and exon 1 of CES1 were sequenced by Sanger and Ion Torrent sequencing to identify gene translocations. The effects of CES1 5'UTRs on mRNA and protein expression were assessed by quantitative real-time PCR, allelic ratio mRNA analysis by primer extension (SNaPshot), quantitative targeted proteomics, and luciferase reporter gene assays.
  
  
  RESULTS
  Sequencing of CES1 identified two translocations: first, CES1VAR (17% minor allele frequency) comprising the 5'UTR, exon 1, and part of intron 1. A second shorter translocation, CES1SVAR, was observed excluding exon 1 and intron 1 regions (<0.01% minor allele frequency). CES1VAR is associated with 2.6-fold decreased CES1 mRNA and ∼1.35-fold lower allelic mRNA. Luciferase reporter constructs showed that CES1VAR decreases luciferase activity 1.5-fold, whereas CES1SVAR slightly increases activity. CES1VAR was not associated with CES1 protein expression or metabolism of the CES1 substrates enalapril, clopidogrel, or methylphenidate in the liver.
  
  
  CONCLUSIONS
  The frequent translocation variant CES1VAR reduces mRNA expression of CES1 in the liver by ∼30%, but protein expression and metabolizing activity in the liver were not detectably altered - possibly because of variable CES1 expression masking small allelic effects. Whether drug therapies are affected by CES1VAR will require further in-vivo studies.
authors: aCenter for Pharmacogenomics, College of Medicine, The Ohio State University, Columbus, Ohio bDepartment of Clinical Pharmacy, University of Michigan, Ann Arbor, Michigan, USA.
authors: Jonathan C
authors: JC
authors: Sanford
authors: Xinwen
authors: X
authors: Wang
authors: Jian
authors: J
authors: Shi
authors: Elizabeth S
authors: ES
authors: Barrie
authors: Danxin
authors: D
authors: Wang
authors: Hao-Jie
authors: HJ
authors: Zhu
authors: Wolfgang
authors: W
authors: Sadee
mesh_terms: D020121:5' Untranslated Regions; D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D014644:Genetic Variation; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000201:enzymology*; D008297:Male; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D014178:Translocation, Genetic
chemical_list: D020121:5' Untranslated Regions; C121305:CES1P1 protein, human; D002265:Carboxylic Ester Hydrolases; C474609:CES1 protein, human