title: Regulation and expression of the ATP-binding cassette transporter ABCG2 in human embryonic stem cells.
abstract: The expression and function of several multidrug transporters (including ABCB1 and ABCG2) have been studied in human cancer cells and in mouse and human adult stem cells. However, the expression of ABCG2 in human embryonic stem cells (hESCs) remains unclear. Limited and contradictory results in the literature from two research groups have raised questions regarding its expression and function. In this study, we used quantitative real-time PCR, Northern blots, whole genome RNA sequencing, Western blots, and immunofluorescence microscopy to study ABCG2 expression in hESCs. We found that full-length ABCG2 mRNA transcripts are expressed in undifferentiated hESC lines. However, ABCG2 protein was undetectable even under embryoid body differentiation or cytotoxic drug induction. Moreover, surface ABCG2 protein was coexpressed with the differentiation marker stage-specific embryonic antigen-1 of hESCs, following constant BMP-4 signaling at days 4 and 6. This expression was tightly correlated with the downregulation of two microRNAs (miRNAs) (i.e., hsa-miR-519c and hsa-miR-520h). Transfection of miRNA mimics and inhibitors of these two miRNAs confirmed their direct involvement in the regulation ABCG2 translation. Our findings clarify the controversy regarding the expression of the ABCG2 gene and also provide new insights into translational control of the expression of membrane transporter mRNAs by miRNAs in hESCs.
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Raji
authors.initials: R
authors.lastname: Padmanabhan
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Chen
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Gillet
authors.forename: Misty
authors.initials: M
authors.lastname: Handley
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Mallon
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Hamilton
authors.forename: Kyeyoon
authors.initials: K
authors.lastname: Park
authors.forename: Sudhir
authors.initials: S
authors.lastname: Varma
authors.forename: Michele G
authors.initials: MG
authors.lastname: Mehaffey
authors.forename: Pamela G
authors.initials: PG
authors.lastname: Robey
authors.forename: Ronald D G
authors.initials: RD
authors.lastname: McKay
authors.forename: Michael M
authors.initials: MM
authors.lastname: Gottesman
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism*; D061252:Feeder Cells; D005347:Fibroblasts; D005786:Gene Expression Regulation; D006801:Humans; D016256:Lewis X Antigen / Q000235:genetics / Q000378:metabolism; D051379:Mice; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis*; D014162:Transfection
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C525809:BMP4 protein, human; D055415:Bone Morphogenetic Protein 4; D016256:Lewis X Antigen; C546194:MIRN519 microRNA, human; C575048:MIRN520 microRNA, human; D035683:MicroRNAs; D009363:Neoplasm Proteins; D012333:RNA, Messenger