Related Experiment Video
Updated: Feb 17, 2026

Methods to Discover Alternative Promoter Usage and Transcriptional Regulation of Murine Bcrp1
Published on: May 27, 2016
Differential effect of ABCB1 haplotypes on promoter activity
Jordan T Speidel1,2, Meixiang Xu2, Sherif Z Abdel-Rahman2
1Department of Biochemistry and Molecular Biology.
Objective:
Promoter single-nucleotide polymorphisms (SNPs) of the ABCB1 gene, encoding the placental efflux transporter P-glycoprotein, can affect its expression and alter xenobiotic transfer from the maternal to the fetal circulation. Because SNPs are arranged in specific combinations as defined haplotypes, the aims of this study were to: (i) determine the placental haplotype structure of the ABCB1 promoter and (ii) determine the differential effect of these haplotypes on placental ABCB1 promoter activity.
Materials And Methods:
DNA samples from 100 healthy placentas were PCR-amplified and sequenced to identify existing SNPs in the proximal ABCB1 promoter. The haplotype structure encompassing these SNPs was inferred by PHASE analysis. Luciferase reporter constructs representing these haplotypes were generated and transfected into human placental 3A cells and their effect on ABCB1 promoter activity was determined using a dual-luciferase assay.
Results:
We identified 12 ABCB1 promoter SNPs. These SNPs were predicted by PHASE to segregate into 28 haplotypes with frequencies ranging between 0.019 and 0.88. We found 12 of these haplotypes in our population in addition to two haplotypes not predicted by PHASE. We also generated two haplotypes to determine individual SNP effects for a total of 16 studied. Compared with the ancestral haplotype, three haplotypes significantly up-regulated (107-266% increase; P<0.05), one significantly down-regulated (95.4% decrease; P<0.01), and 12 had no statistically significant effect on ABCB1 promoter activity.
Discussion And Conclusion:
Our data show that the effect of SNPs on promoter activity depends on their presence in a specific haplotype. This indicates that haplotypes, rather than individual SNPs, could play a significant role in regulating placental P-glycoprotein expression and affect placental transfer and fetal exposure to xenobiotics.
Related Concept Videos
Pharmacogenetics of Drug Transporters: P-Glycoprotein and Solute Carrier Transporters
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase
ABC Transporters: Exporter
Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu
The Eukaryotic Promoter Region
Cell Specific Gene Expression

