6-Thioguanine Reactivates Epigenetically Silenced Genes in Acute Lymphoblastic Leukemia Cells by Facilitating Proteasome-mediated Degradation of DNMT1

Yuan, Bi-Feng; Zhang, Jing; Wang, Hongxia; Xiong, Lei; Cai, Qian; Wang, Tina; Jacobsen, Steven E.; Pradhan, Sriharsa; Wang, Yinsheng

doi:10.1158/0008-5472.can-10-3430

Cited by 43 publications

(38 citation statements)

References 49 publications

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“…The resulting 28 nucleosides were then further analyzed by liquid chromatography-electrospray 29 ionization-tandem mass spectrometry (LC-ESI-MS/MS). With the developed method, 30 we are able to detect DNA and RNA methylation (5-methyl-2'-deoxycytidine, 31 5-methylcytidine, and N 6 -methyladenosine) in a single cell. We then further 32 successfully determined DNA and RNA methylation in CTCs from lung cancer 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 INTRODUCTION 48 DNA cytosine methylation (5-methyl-2'-deoxycytidine, 5-mdC) is one of the 49 most important epigenetic marks that play critical roles in a variety of cellular 50 processes, 1 including cell differentiation, 2 genome imprinting, 3 and X-chromosome 51 inactivation.…”

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confidence: 99%

Determination of DNA and RNA Methylation in Circulating Tumor Cells by Mass Spectrometry

et al. 2016

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DNA methylation (5-methylcytosine, 5-mC) is the best characterized epigenetic mark that has regulatory roles in diverse biological processes. Recent investigation of RNA modifications also raises the possible functions of RNA adenine and cytosine methylations on gene regulation in the form of "RNA epigenetics." Previous studies demonstrated global DNA hypomethylation in tumor tissues compared to healthy controls. However, DNA and RNA methylation in circulating tumor cells (CTCs) that are derived from tumors are still a mystery due to the lack of proper analytical methods. In this respect, here we established an effective CTCs capture system conjugated with a combined strategy of sample preparation for the captured CTCs lysis, nucleic acids digestion, and nucleosides extraction in one tube. The resulting nucleosides were then further analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). With the developed method, we are able to detect DNA and RNA methylation (5-methyl-2'-deoxycytidine, 5-methylcytidine, and N(6)-methyladenosine) in a single cell. We then further successfully determined DNA and RNA methylation in CTCs from lung cancer patients. Our results demonstrated, for the first time, a significant decrease of DNA methylation (5-methyl-2'-deoxycytidine) and increase of RNA adenine and cytosine methylations (N(6)-methyladenosine and 5-methylcytidine) in CTCs compared with whole blood cells. The discovery of DNA hypomethylation and RNA hypermethylation in CTCs in the current study together with previous reports of global DNA hypomethylation in tumor tissues suggest that nucleic acid modifications play important roles in the formation and development of cancer cells. This work constitutes the first step for the investigation of DNA and RNA methylation in CTCs, which may facilitate uncovering the metastasis mechanism of cancers in the future.

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Determination of DNA and RNA Methylation in Circulating Tumor Cells by Mass Spectrometry

et al. 2016

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“…27 Demethylation of DNMT1 by LSD1 stabilizes the enzyme from protein degrading and is essential for maintaining global DNA methylation in embryonic stem (ES) cells. 28,29 Interestingly, many types of cancer show upregulation of both DNMT1 and LSD1, but a real link between the 2 epigenetic enzymes in such pathologies has to be established. The retinoblastoma protein 1 (RB1) regulator myosin phosphatase target subunit 1 (MYPT1) is also demethylated by LSD1 at Lys442, losing in such way its stability and leading to enhancement of RB1 phosphorylation.…”

Section: The Lys-specific Demethylase Lsd1mentioning

confidence: 99%

Targeting Histone Demethylases: A New Avenue for the Fight against Cancer

2011

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In addition to genetic disorders, epigenetic alterations have been shown to be involved in cancer, through misregulation of histone modifications. Miswriting, misreading, and mis-erasing of histone acetylation as well as methylation marks can be actually associated with oncogenesis and tumor proliferation. Historically, methylation of Arg and Lys residues has been considered a stable, irreversible process due to the slow turnover of methyl groups in chromatin. The discovery in recent years of a large number of histone Lys demethylases (KDMs, belonging to either the amino oxidase or the JmjC family) totally changed this point of view and suggested a new role for dynamic histone methylation in biological processes. Since overexpression, alteration, or mutation of a number of KDMs has been found in many types of cancers, such enzymes could represent diagnostic tools as well as epigenetic targets to modulate for obtaining novel therapeutic weapons against cancer. The first little steps in this direction are described here.

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“…11 Subsequent studies showed that proteasomal degradation of DNMT1 occurs under normal physiological conditions 12 and in response to a variety of drugs. [13][14][15][16] Recently, our laboratory has shown that a quinoline-based drug, designated SGI-1027, impedes the activity of all 3 DNA methyltransferases by competing with S-adenosyl methionine and induces selective proteasomal degradation of DNMT1, causing DNA hypomethylation and reexpression of the silenced tumor suppressor genes. 17 Degradation of DNMT1 is dependent on the conserved KEN box, BAH (bromo-adjacent homology) domains, and its nuclear localization.…”

Section: Introductionmentioning

confidence: 99%

Novel Insights into the Molecular Mechanism of Action of DNA Hypomethylating Agents: Role of Protein Kinase C in Decitabine-Induced Degradation of DNA Methyltransferase 1

et al. 2012

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We have previously demonstrated proteasomal degradation of DNMT1 in mammalian cells following treatment with several DNA hypomethylating agents. Here, we demonstrate dose-dependent degradation of Dnmt1 in mouse embryonic stem (ES) cells expressing catalytic site mutant (cysser), confirming that the covalent bond formation between Dnmt1 and decitabine-incorporated DNA is not essential for this process. DNMT1o, the oocyte-specific isoform that lacks the N-terminal 118-amino acid domain, did not undergo decitabine-mediated degradation, which further proves the requirement of multiple domains including nuclear localization signal, KEN box, and BAH domains for this process. Analysis of glycerol density gradient fractions of micrococcal nuclease-digested nuclei showed that both nucleosomal and nucleoplasmic DNMT1 are degraded upon decitabine treatment. Among different inhibitors tested, the inhibitors of the proteasomal pathway and several protein kinases impeded decitabineinduced DNMT1 degradation. The maximal effect caused by inhibiting protein kinase C (PKC) persuaded us to investigate further its role in decitabine-mediated DNMT1 degradation. Blockage of the degradation process after treatment with rottlerin, an inhibitor of PKCδ, or after siRNAmediated depletion of PKCδ, indicated that this protein kinase is involved in decitabine-mediated depletion of DNMT1. PKCδ interacted with and phosphorylated DNMT1 in vitro. Moreover, rottlerin inhibited both basal and decitabine-induced phosphorylation of DNMT1. These studies provide substantial evidence that decitabine-induced degradation of the maintenance methyltransferase DNMT1 does not require covalent bond formation with the substrate and also elucidate its underlying molecular mechanism.

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6-Thioguanine Reactivates Epigenetically Silenced Genes in Acute Lymphoblastic Leukemia Cells by Facilitating Proteasome-mediated Degradation of DNMT1

Cited by 43 publications

References 49 publications

Determination of DNA and RNA Methylation in Circulating Tumor Cells by Mass Spectrometry

Determination of DNA and RNA Methylation in Circulating Tumor Cells by Mass Spectrometry

Targeting Histone Demethylases: A New Avenue for the Fight against Cancer

Novel Insights into the Molecular Mechanism of Action of DNA Hypomethylating Agents: Role of Protein Kinase C in Decitabine-Induced Degradation of DNA Methyltransferase 1

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