Human sulfotransferase SULT2A1 pharmacogenetics: genotype-to-phenotype studies

Abstract

SULT2A1 catalyzes the sulfate conjugation of dehydroepiandrosterone (DHEA) as well as other steroids. As a step toward pharmacogenetic studies, we have 'resequenced' SULT2A1 using 60 DNA samples from African-American and 60 samples from Caucasian-American subjects. All exons, splice junctions and approximately 370 bp located 5' of the site of transcription initiation were sequenced. We observed 15 single nucleotide polymorphisms (SNPs), including three non-synonymous coding SNPs (cSNPs) that were present only in DNA from African-American subjects. Linkage analysis revealed that two of the nonsynonymous cSNPs were tightly linked. Expression constructs were created for all nonsynonymous cSNPs observed, including a 'double variant' construct that included the two linked cSNPs, and those constructs were expressed in COS-1 cells. SULT2A1 activity was significantly decreased for three of the four variant allozymes. Western blot analysis demonstrated that decreased levels of immunoreactive protein appeared to be the major mechanism responsible for decreases in activity, although apparent Km values also varied among the recombinant allozymes. In addition, the most common of the nonsynonymous cSNPs disrupted the portion of SULT2A1 involved with dimerization, and this variant allozyme behaved as a monomer rather than a dimer during gel filtration chromatography. These observations indicate that common genetic polymorphisms for SULT2A1 can result in reductions in levels of both activity and enzyme protein. They also raise the possibility of ethnic-specific pharmacogenetic variation in SULT2A1-catalyzed sulfation of both endogenous and exogenous substrates for this phase II drug-metabolizing enzyme.

Pharmacogenetics of human cytosolic sulfotransferases

“…The frequencies of the G187C and G781A variants in the AR and AL populations were similar to those reported by Thomae et al (2002). The presence of the G187C and G781A variants are tightly linked giving rise to essentially three haplotypes.…”

“…Thomae et al (2002) have reported the resequencing and analysis of sequence variants in the SULT2A1 gene of 60 Caucasian and African-Americans (AA) DNA samples obtained from the Coriell Cell Repository. A total of 15 SNPs were identified in the 5 0 -flanking region and intron and exon sequences of the SULT2A1 gene sequenced.…”

“…The nonsynonymous SNPs were detected only in the AA DNA samples, suggesting a racial difference in SULT2A1 expression and activity. The allelic frequencies reported by Thomae et al (2002) in 120 alleles from the Coriell Cell Repositorty are shown in Table 3. The G187C and G781A variants were present in multiple copies in the Coriell samples whereas only a single A679G variant was detected.…”

Thiopurine S-methyltransferase pharmacogenetics: insights, challenges and future directions

“…Specifically, Figure 4 show that there was a highly significant correlation between level of enzyme activity and quantity of immunoreactive protein in these variant allozymes -ranging from high values for the WT sequence to virtually no protein for TPMT*3A . This phenomenon has also been observed for many other common genetic polymorphisms that alter only a single amino acid (Freimuth et al, 2001;Thomae et al, 2002;Adjei et al, 2003;Thomae et al, 2003;Weinshilboum and Wang, 2004a;Ji et al, 2005). Of the allozymes studied by Salavaggione et al (2005), TPMT*3A, *3B, *3C and *2 displayed the most striking effects.…”

Human cytosolic sulfotransferase database mining: identification of seven novel genes and pseudogenes

“…[31][32][33] More recently, a series of gene resequencing and functional genomic studies have resulted in the identification of functionally significant genetic polymorphisms for SULT1A1, 34 SULT1A3, 35 SULT1E1, 36 and SULT2A1. 37 One of the SULT1A1 polymorphisms has already been reported to be of pharmacogenetic significance for variation in the survival of breast cancer patients treated with tamoxifen. 38 Therefore, it is important for pharmacogenetics that all human genes encoding cytosolic SULTs be identified and characterized.…”