Alternative Polyadenylation of ABC Transporters of the C-Family (ABCC1, ABCC2, ABCC3) and Implications on Posttranscriptional Micro-RNA Regulation

Abstract

ATP-binding cassette (ABC) transporters represent a large group of efflux pumps that are strongly involved in the pharmacokinetics of various drugs and nutrient distribution. It was recently shown that micro-RNAs (miRNAs) may significantly alter their expression as proven, e.g., for miR-379 and ABCC2. However, alternative mRNA polyadenylation may result in expression of 39-untranslated regions (39-UTRs) with varying lengths. Thus, length variants may result in presence or absence of miRNA binding sites for regulatory miRNAs with consequences on posttranscriptional control. In the present study, we report on 39-UTR variants of ABCC1, ABCC2, and ABCC3 mRNA. Applying in vitro luciferase reporter gene assays, we show that expression of short ABCC2 39-UTR variants leads to a significant loss of miR-379/ABCC2 interaction and subsequent upregulation of ABCC2 expression. Furthermore, we show that expression of ABCC2 39-UTR lengths varies significantly between human healthy tissues but is not directly correlated to the respective protein level in vivo. In conclusion, the presence of altered 39-UTR lengths in ABC transporters could lead to functional consequences regarding posttranscriptional gene expression, potentially regulated by alternative polyadenylation. Hence, 39-UTR length variability may be considered as a further mechanism contributing to variability of ABCC transporter expression and subsequent drug variation in drug response.SIGNIFICANCE STATEMENT micro-RNA (miRNA) binding to 39-untranslated region (39-UTR) plays an important role in the control of ATP-binding cassette (ABC)-transporter mRNA degradation and translation into proteins. We disclosed various 39-UTR length variants of ABCC1, C2, and C3 mRNA, with loss of mRNA seed regions partly leading to varying and tissue-dependent interaction with miRNAs, as proven by reporter gene assays. Alternative 39-UTR lengths may contribute to variable ABCC transporter expression and potentially explains inconsistent findings in miRNA studies.

Quercetin and Isorhamnetin Attenuate Benzo[a]pyrene-Induced Toxicity by Modulating Detoxification Enzymes through the AhR and NRF2 Signaling Pathways

“…The ABCC transporter, known as phase III enzymes, is one of the proteins that are significantly affected by posttranscriptional regulation. Especially, micro-RNAs(miRNAs) extensively affect their protein level through interaction with target mRNA [ 38 ]. Previous research reported B[a]P induces the mRNA expression of ABCCs, while inhibiting the protein level and function of ABCC transporters [ 39 , 40 ].…”

Genome‑wide expression and methylation analyses reveal aberrant cell adhesion signaling in tyrosine kinase inhibitor‑resistant CML cells

“…Whole cell lysates and immunoblotting. Whole cell lysates and immunoblotting were performed as previously described (17,23,24) Cell adhesion assay. Corning Matrigel basement membrane mix (VWR) was thawed overnight at 4˚C.…”

Pharmacogenetics of Carbamazepine and Valproate: Focus on Polymorphisms of Drug Metabolizing Enzymes and Transporters

“…Several adenosine triphosphate (ATP)-dependent proteins, such as the ATP-binding cassette (ABC) transporter superfamily, have been associated with drug resistance, metabolism, and toxicity [ 111 ]. Several polymorphisms of the main ABC transporters of P-glycoprotein ( MDR1 , ABCB1 ) and multiple resistance-associated protein 2 ( MRP , ABCC2 ) influence drug bioavailability and clinical response [ 112 , 113 ]. Alterations in ABC transporter efflux could limit central distribution of many psychotropic drugs, such as CBZ [ 114 ].…”