title: Human N-acetyltransferase 1 *10 and *11 alleles increase protein expression through distinct mechanisms and associate with sulfamethoxazole-induced hypersensitivity.
abstract: OBJECTIVE
  N-acetyltransferase 1 (NAT1) metabolizes drugs and environmental carcinogens. NAT1 alleles *10 and *11 have been proposed to alter protein level or enzyme activity compared with wild-type NAT1 *4 and to confer cancer risk, through uncertain pathways. This study characterizes regulatory polymorphisms and underlying mechanisms of NAT1 expression.
  
  
  METHODS
  We measured allelic NAT1 mRNA expression and translation, as a function of multiple transcription start sites, alternative splicing, and three 3'-polyadenylation sites in human livers (one of which was discovered in this study), B lymphocytes, and transfected cells. In a clinical study of 469 patients with HIV/AIDS treated with the NAT1/NAT2 substrate sulfamethoxazole (SMX), associations were tested between SMX-induced hypersensitivity and NAT1 *10 and *11 genotypes, together with known NAT2 polymorphisms.
  
  
  RESULTS
  NAT1 *10 and *11 were determined to act as common regulatory alleles accounting for most NAT1 expression variability, both leading to increased translation into active protein. NAT1 *11 (2.4% minor allele frequency) affected 3'-polyadenylation site usage, thereby increasing formation of NAT1 mRNA with intermediate length 3'-untranslated region (major isoform) at the expense of the short isoform, resulting in more efficient protein translation. NAT1 *10 (19% minor allele frequency) increased translation efficiency without affecting 3'-untranslated region polyadenylation site usage. Livers and B-lymphocytes with *11/*4 and *10/*10 genotypes displayed higher NAT1 immunoreactivity and NAT1 enzyme activity than the reference genotype *4/*4. Patients who carry *10/*10 and *11/*4 (fast NAT1 acetylators) were less likely to develop hypersensitivity to SMX, but this was observed only in individuals who are also carrying a slow NAT2 acetylator genotype.
  
  
  CONCLUSIONS
  NAT1 *10 and *11 significantly increase NAT1 protein level/enzyme activity, enabling the classification of carriers into reference and rapid acetylators. Rapid NAT1 acetylator status seems to protect against SMX toxicity by compensating for slow NAT2 acetylator status.
authors: Department of Pharmacology, Program in Pharmacogenomics, School of Biomedical Science, Ohio State University, Columbus, Ohio 43210, USA. wang.808@osu.edu
authors: Danxin
authors: D
authors: Wang
authors: Michael F
authors: MF
authors: Para
authors: Susan L
authors: SL
authors: Koletar
authors: Wolfgang
authors: W
authors: Sadee
mesh_terms: D000107:Acetylation; D000483:Alleles; D001191:Arylamine N-Acetyltransferase / Q000235:genetics* / Q000378:metabolism; D001402:B-Lymphocytes / Q000378:metabolism; D005786:Gene Expression Regulation; D005787:Gene Frequency; D057809:HEK293 Cells; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D011110:Polymorphism, Genetic; D039104:RNA 3' Polyadenylation Signals; D022821:RNA Splice Sites; D012333:RNA, Messenger / Q000235:genetics*; D013420:Sulfamethoxazole / Q000494:pharmacology* / Q000633:toxicity; D024363:Transcription Initiation Site
chemical_list: D007527:Isoenzymes; D022821:RNA Splice Sites; D012333:RNA, Messenger; D001191:Arylamine N-Acetyltransferase; C089384:N-acetyltransferase 1; C478900:NAT2 protein, human; D013420:Sulfamethoxazole