title: Identification and characterization of proximal promoter polymorphisms in the human concentrative nucleoside transporter 2 (SLC28A2).
abstract: The human concentrative nucleoside transporter 2 (CNT2) plays an important role in the absorption, disposition, and biological effects of endogenous nucleosides and nucleoside analog drugs. We identified genetic variation in the basal promoter region of CNT2 and characterized the function of the variants. We screened DNA from an ethnically diverse population and identified five basal promoter variants in CNT2. Three major haplotypes in the CNT2 basal promoter region were identified and were found at different allele frequencies in various ethnic groups. The common promoter variants and haplotypes were constructed and characterized for their promoter activity using luciferase reporter assays. One polymorphic variant, rs2413775 (-146T>A), with an allele frequency >20% in all populations, showed a gain of function in luciferase activity. Furthermore, in vivo mouse promoter assays of these nucleotide variants using the hydrodynamic tail vein injection, leading to their expression in the liver, demonstrated similar results. Transcription factor binding site (TFBS) analysis indicated this variant alters a hepatic nuclear factor (HNF) 1 TFBS. Electrophoretic mobility shift assay demonstrated stronger binding of HNF1alpha and weaker binding of HNF1beta to the -146T and -146A regions, whereas the single nucleotide polymorphism (SNP), -146A, exhibited enhanced binding to both HNF1alpha and HNF1beta, consistent with its greater activity in reporter assays. The data collectively suggest that the common variant, -146T>A, in the proximal promoter of CNT2 may result in an enhanced transcription rate of the gene and, thus, expression levels of CNT2. This SNP may play a role in variation in the pharmacokinetics and pharmacological effects of nucleoside analogs.
authors.affiliation: Department of Biopharmaceutical Sciences, University of California, 1550 4th Street, RH584, Box 2911, San Francisco, CA 94158-2911, USA.
authors.forename: Sook Wah
authors.initials: SW
authors.lastname: Yee
authors.forename: James E
authors.initials: JE
authors.lastname: Shima
authors.forename: Stephanie
authors.initials: S
authors.lastname: Hesselson
authors.forename: Loan
authors.initials: L
authors.lastname: Nguyen
authors.forename: Sarah
authors.initials: S
authors.lastname: De Val
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Lafond
authors.forename: Michiko
authors.initials: M
authors.lastname: Kawamoto
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Johns
authors.forename: Doug
authors.initials: D
authors.lastname: Stryke
authors.forename: Pui-Yan
authors.initials: PY
authors.lastname: Kwok
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Ferrin
authors.forename: Brian L
authors.initials: BL
authors.lastname: Black
authors.forename: David
authors.initials: D
authors.lastname: Gurwitz
authors.forename: Nadav
authors.initials: N
authors.lastname: Ahituv
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Giacomini
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005006:Ethnicity / Q000235:genetics; D005787:Gene Frequency; D014644:Genetic Variation; D006801:Humans; D026901:Membrane Transport Proteins / Q000187:drug effects / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D009705:Nucleosides / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D026901:Membrane Transport Proteins; D009705:Nucleosides; C065171:cif nucleoside transporter; D004247:DNA