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Open AccessArticle

Identification of PARP-1, Histone H1 and SIRT-1 as New Regulators of Breast Cancer-Related Aromatase Promoter I.3/II

1
Institute for Biochemistry II, Jena University Hospital, Friedrich Schiller University, 07743 Jena, Germany
2
Department of Internal Medicine II, Jena University Hospital, Friedrich Schiller University, 07743 Jena, Germany
3
Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute (HKI), 07745 Jena, Germany
4
Department of Gynecology and Obstetrics, Robert-Koch-Hospital, 99510 Apolda, Germany
*
Author to whom correspondence should be addressed.
Cells 2020, 9(2), 427; https://doi.org/10.3390/cells9020427
Received: 22 January 2020 / Revised: 6 February 2020 / Accepted: 10 February 2020 / Published: 12 February 2020
(This article belongs to the Special Issue Molecular and Cellular Mechanisms of Cancers: Breast Cancer)
Paracrine interactions between malignant estrogen receptor positive (ER+) breast cancer cells and breast adipose fibroblasts (BAFs) stimulate estrogen biosynthesis by aromatase in BAFs. In breast cancer, mainly the cAMP-responsive promoter I.3/II-region mediates excessive aromatase expression. A rare single nucleotide variant (SNV) in this promoter region, which caused 70% reduction in promoter activity, was utilized for the identification of novel regulators of aromatase expression. To this end, normal and mutant promoter activities were measured in luciferase reporter gene assays. DNA-binding proteins were captured by DNA-affinity and identified by mass spectrometry. The DNA binding of proteins was analyzed using electrophoretic mobility shift assays, immunoprecipitation-based in vitro binding assays and by chromatin immunoprecipitation in BAFs in vivo. Protein expression and parylation were analyzed by western blotting. Aromatase activities and RNA-expression were measured in BAFs. Functional consequences of poly (ADP-ribose) polymerase-1 (PARP-1) knock-out, rescue or overexpression, respectively, were analyzed in murine embryonic fibroblasts (MEFs) and the 3T3-L1 cell model. In summary, PARP-1 and histone H1 (H1) were identified as critical regulators of aromatase expression. PARP-1-binding to the SNV-region was crucial for aromatase promoter activation. PARP-1 parylated H1 and competed with H1 for DNA-binding, thereby inhibiting its gene silencing action. In MEFs (PARP-1 knock-out and wild-type) and BAFs, PARP-1-mediated induction of the aromatase promoter showed bi-phasic dose responses in overexpression and inhibitor experiments, respectively. The HDAC-inhibitors butyrate, panobinostat and selisistat enhanced promoter I.3/II-mediated gene expression dependent on PARP-1-activity. Forskolin stimulation of BAFs increased promoter I.3/II-occupancy by PARP-1, whereas SIRT-1 competed with PARP-1 for DNA binding but independently activated the promoter I.3/II. Consistently, the inhibition of both PARP-1 and SIRT-1 increased the NAD+/NADH-ratio in BAFs. This suggests that cellular NAD+/NADH ratios control the complex interactions of PARP-1, H1 and SIRT-1 and regulate the interplay of parylation and acetylation/de-acetylation events with low NAD+/NADH ratios (reverse Warburg effect), promoting PARP-1 activation and estrogen synthesis in BAFs. Therefore, PARP-1 inhibitors could be useful in the treatment of estrogen-dependent breast cancers.
Keywords: breast cancer; estrogen synthesis; breast adipose fibroblasts; adipose stromal cells; epigenetics; SIRT-1; PARP-1 breast cancer; estrogen synthesis; breast adipose fibroblasts; adipose stromal cells; epigenetics; SIRT-1; PARP-1
MDPI and ACS Style

Kaiser, A.; Krüger, T.; Eiselt, G.; Bechler, J.; Kniemeyer, O.; Huber, O.; Schmidt, M. Identification of PARP-1, Histone H1 and SIRT-1 as New Regulators of Breast Cancer-Related Aromatase Promoter I.3/II. Cells 2020, 9, 427.

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