Abstract
ABCG2 encodes the mitoxantrone resistance protein (MXR; breast cancer resistance protein), an ATP-binding cassette (ABC) efflux membrane transporter. Computational analysis of the ∼300 kb region of DNA surrounding ABCG2 (chr4:88911376-89220011, hg19) identified 30 regions with potential cis-regulatory capabilities. These putative regulatory regions were tested for their enhancer and suppressor activity in a human liver cell line using luciferase reporter assays. The in vitro enhancer and suppressor assays identified four regions that decreased gene expression and five regions that increased expression >1.6-fold. Four of five human hepatic in vitro enhancers were confirmed as in vivo liver enhancers using the mouse hydrodynamic tail vein injection assay. Two of the in vivo liver enhancers (ABCG2RE1 and ABCG2RE9) responded to 17β-estradiol or rifampin in human cell lines, and ABCG2RE9 had ChIP-seq evidence to support the binding of several transcription factors and the transcriptional coactivator p300 in human hepatocytes. This study identified genomic regions surrounding human ABCG2 that can function as regulatory elements, some with the capacity to alter gene expression upon environmental stimulus. The results from this research will drive future investigations of interindividual variation in ABCG2 expression and function that contribute to differences in drug response.
Footnotes
- Received June 13, 2016.
- Accepted November 2, 2016.
These studies were supported by the National Institutes of Health [Grant U01-GM-61390] (to N.A. and D.L.K.), the National Human Genome Research Institute [Grants R01-HG-006768 and R01-HG-005058] (to N.A.), the Eunice Kennedy Shriver National Institute of Child Health and Human Development [Grant R01-HD-059862] (to N.A.), the National Institute of Neurologic Disorders and Stroke [Grant R01-NS-079231] (to R.P.S. and N.A.), the National Institute of Diabetes and Digestive and Kidney Diseases [Grant R01-DK-090382] (to N.A.), the National Institute of General Medical Sciences Predoctoral Training Grant [T32-GM-007175] (to R.J.E., M.J.K., and X.L.); and were part of the Pharmacogenetics of Membrane Transporters project in the Pharmacogenetics Research Network. R.J.E. was supported by an American Foundation for Pharmaceutical Education Predoctoral fellowship; M.J.K. was supported in part by the University of California, San Francisco, Quantitative Biosciences Consortium fellowship for Interdisciplinary Research and the Amgen Research Excellence in Bioengineering and Therapeutic Sciences fellowship; and R.P.S. was partially supported by a Canadian Institute of Health Research Fellowship in Hepatology.
↵This article has supplemental material available at dmd.aspetjournals.org.
- Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|