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author:("Wang, danxi")
1.  Human N-acetyltransferase 1 (NAT1) *10 and *11 alleles increase protein expression via distinct mechanisms and associate with sulfamethoxazole-induced hypersensitivity 
Pharmacogenetics and genomics  2011;21(10):652-664.
Objectives
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 to wild-type NAT1 *4 and to confer cancer risk, via 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 discovered in this study), B lymphocytes, and transfected cells. In a clinical study of 469 HIV/AIDS patients 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′UTR (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′-UTR 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 subjects also carrying a slow NAT2 acetylator genotype.
Conclusion
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 appears to protect against SMX toxicity by compensating for slow NAT2 acetylator status.
doi:10.1097/FPC.0b013e3283498ee9
PMCID: PMC3172334  PMID: 21878835
N-acetyltransferase; NAT1; polyadenylation; allelic expression imbalance; sulfamethoxazole; cotrimoxazole; protein translation; acetylator phenotype; idiosyncratic drug reactions

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