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Project description:BackgroundUbiquitin-like protein containing PHD and RING finger domains 1 (UHRF1) is a major regulator of epigenetic mechanisms and is overexpressed in various human malignancies. In this study, we examined the involvement of UHRF1 in aberrant DNA methylation and gene silencing in colorectal cancer (CRC).ResultsCRC cell lines were transiently transfected with siRNAs targeting UHRF1, after which DNA methylation was analyzed using dot blots, bisulfite pyrosequencing, and Infinium HumanMethylation450 BeadChip assays. Gene expression was analyzed using RT-PCR and gene expression microarrays. Depletion of UHRF1 rapidly induced genome-wide DNA demethylation in CRC cells. Infinium BeadChip assays and bisulfite pyrosequencing revealed significant demethylation across entire genomic regions, including CpG islands, gene bodies, intergenic regions, and repetitive elements. Despite the substantial demethylation, however, UHRF1 depletion only minimally reversed CpG island hypermethylation-associated gene silencing. By contrast, the combination of UHRF1 depletion and histone deacetylase (HDAC) inhibition reactivated the silenced genes and strongly suppressed CRC cell proliferation. The combination of UHRF1 depletion and HDAC inhibition also induced marked changes in the gene expression profiles such that cell cycle-related genes were strikingly downregulated.ConclusionsOur results suggest that (i) maintenance of DNA methylation in CRC cells is highly dependent on UHRF1; (ii) UHRF1 depletion rapidly induces DNA demethylation, though it is insufficient to fully reactivate the silenced genes; and (iii) dual targeting of UHRF1 and HDAC may be an effective new therapeutic strategy.
| S-EPMC6505222 | biostudies-literature
Project description:UHRF1 depletion and HDAC inhibition synergistically reactivate epigenetically silenced genes in colorectal cancer cells
| PRJNA416872 | ENA
Project description:Chemicals reactivating epigenetically silenced genes target diverse classes of enzymes, including DNMTs, HDACs, HMTs and BET protein family members. They can strongly influence the expression of genes and endogenous retroviral elements with concomitant dsRNA synthesis and massive transcription of LTRs. Chemicals reactivating gene expression may cause both beneficial effects in cancer cells and may be hazardous by promoting carcinogenesis. Among chemicals used in medicine and commerce, only a small fraction has been studied with respect to their influence on epigenetic silencing. Screening of chemicals reactivating silent genes requires adequate systems mimicking whole-genome processes. We used a HeLa TSA-inducible cell population (HeLa TI cells) obtained by retroviral infection of a GFP-containing vector followed by several rounds of cell sorting for screening purposes. Previously, the details of GFP epigenetic silencing in HeLa TI cells were thoroughly described. Herein, we show that the epigenetically repressed gene GFP is reactivated by 15 agents, including HDAC inhibitors-vorinostat, sodium butyrate, valproic acid, depsipeptide, pomiferin, and entinostat; DNMT inhibitors-decitabine, 5-azacytidine, RG108; HMT inhibitors-UNC0638, BIX01294, DZNep; a chromatin remodeler-curaxin CBL0137; and BET inhibitors-JQ-1 and JQ-35. We demonstrate that combinations of epigenetic modulators caused a significant increase in cell number with reactivated GFP compared to the individual effects of each agent. HeLa TI cells are competent to metabolize xenobiotics and possess constitutively expressed and inducible cytochrome P450 mono-oxygenases involved in xenobiotic biotransformation. Thus, HeLa TI cells may be used as an adequate test system for the extensive screening of chemicals, including those that must be metabolically activated. Studying the additional metabolic activation of xenobiotics, we surprisingly found that the rat liver S9 fraction, which has been widely used for xenobiotic activation in genotoxicity tests, reactivated epigenetically silenced genes. Applying the HeLa TI system, we show that N-nitrosodiphenylamine and N-nitrosodimethylamine reactivate epigenetically silenced genes, probably by affecting DNA methylation.
| S-EPMC8195432 | biostudies-literature
Project description:UHRF1 is a major regulator of epigenetic mechanism and is overexpressed in various human malignancies. In this study, we examined the involvement of UHRF1 in aberrant DNA methylation in colorectal cancer (CRC). In CRC cells, transient UHRF1 knockdown rapidly induced DNA demethylation across entire genomic regions, including CpG islands, gene bodies and repetitive elements. Nonetheless, UHRF1 depletion only minimally reversed CpG island hypermethylation-associated gene silencing. However, the combination of UHRF1 depletion and histone deacetylase (HDAC) inhibition synergistically reactivated the silenced genes and strongly suppressed CRC cell proliferation. Our results suggest that (i) maintenance of DNA methylation in CRC cells is highly dependent on UHRF1; (ii) UHRF1 depletion rapidly induces DNA demethylation, though it is insufficient to fully reactivate the silenced genes; and (iii) dual targeting of UHRF1 and HDAC may be an effective new therapeutic strategy.
2019-05-21 | GSE113664 | GEO
Project description:UHRF1 is a major regulator of epigenetic mechanism and is overexpressed in various human malignancies. In this study, we examined the involvement of UHRF1 in aberrant DNA methylation in colorectal cancer (CRC). In CRC cells, transient UHRF1 knockdown rapidly induced DNA demethylation across entire genomic regions, including CpG islands, gene bodies and repetitive elements. Nonetheless, UHRF1 depletion only minimally reversed CpG island hypermethylation-associated gene silencing. However, the combination of UHRF1 depletion and histone deacetylase (HDAC) inhibition synergistically reactivated the silenced genes and strongly suppressed CRC cell proliferation. Our results suggest that (i) maintenance of DNA methylation in CRC cells is highly dependent on UHRF1; (ii) UHRF1 depletion rapidly induces DNA demethylation, though it is insufficient to fully reactivate the silenced genes; and (iii) dual targeting of UHRF1 and HDAC may be an effective new therapeutic strategy.
2019-05-21 | GSE106437 | GEO
Project description:UHRF1 is a major regulator of epigenetic mechanism and is overexpressed in various human malignancies. In this study, we examined the involvement of UHRF1 in aberrant DNA methylation in colorectal cancer (CRC). In CRC cells, transient UHRF1 knockdown rapidly induced DNA demethylation across entire genomic regions, including CpG islands, gene bodies and repetitive elements. Nonetheless, UHRF1 depletion only minimally reversed CpG island hypermethylation-associated gene silencing. However, the combination of UHRF1 depletion and histone deacetylase (HDAC) inhibition synergistically reactivated the silenced genes and strongly suppressed CRC cell proliferation. Our results suggest that (i) maintenance of DNA methylation in CRC cells is highly dependent on UHRF1; (ii) UHRF1 depletion rapidly induces DNA demethylation, though it is insufficient to fully reactivate the silenced genes; and (iii) dual targeting of UHRF1 and HDAC may be an effective new therapeutic strategy.
2019-05-21 | GSE106402 | GEO
Project description:UHRF1 is a major regulator of epigenetic mechanism and is overexpressed in various human malignancies. In this study, we examined the involvement of UHRF1 in aberrant DNA methylation in colorectal cancer (CRC). In CRC cells, transient UHRF1 knockdown rapidly induced DNA demethylation across entire genomic regions, including CpG islands, gene bodies and repetitive elements. Nonetheless, UHRF1 depletion only minimally reversed CpG island hypermethylation-associated gene silencing. However, the combination of UHRF1 depletion and histone deacetylase (HDAC) inhibition synergistically reactivated the silenced genes and strongly suppressed CRC cell proliferation. Our results suggest that (i) maintenance of DNA methylation in CRC cells is highly dependent on UHRF1; (ii) UHRF1 depletion rapidly induces DNA demethylation, though it is insufficient to fully reactivate the silenced genes; and (iii) dual targeting of UHRF1 and HDAC may be an effective new therapeutic strategy.
2019-05-21 | GSE106438 | GEO
Project description:BackgroundCytosine methylation is involved in epigenetic control of gene expression in a wide range of organisms. An increasing number of examples indicate that changing the frequency of cytosine methylation in the genome is a feasible tool to engineer novel traits in plants. Although demethylating effects of compounds have been analyzed in human cultured cells in terms of suppressing cancer, their effect in plant cells has not been analyzed extensively. Here, we developed in planta assay systems to detect inhibition of cytosine methylation using plants that contain a transgene transcriptionally silenced by an epigenetic mechanism.ResultsSeeds of two transgenic plants were used: a petunia line that has been identified as a revertant of the co-suppression of the chalcone synthase-A (CHS-A) gene and contains CHS-A transgenes whose transcription is repressed; Nicotiana benthamiana plants that contain the green fluorescent protein (GFP) reporter gene whose transcription is repressed through virus-induced transcriptional gene silencing. Seeds of these plants were sown on a medium that contained a demethylating agent, either 5-azacytidine or trichostatin A, and the restoration of the transcriptionally active state of the transgene was detected in seedlings. Using these systems, we found that genistein, a major isoflavonoid compound, inhibits cytosine methylation, thus restoring transgene transcription. Genistein also restored the transcription of an epigenetically silenced endogenous gene in Arabidopsis plants.ConclusionsOur assay systems allowed us to assess the inhibition of cytosine methylation, in particular of maintenance of methylation, by compounds in plant cells. These results suggest a novel role of flavonoids in plant cells and that genistein is useful for modifying the epigenetic state of plant genomes.
| S-EPMC3362751 | biostudies-literature
Project description:Cyclin-dependent kinase 9 (CDK9) promotes transcriptional elongation through RNAPII pause release. We now report that CDK9 is also essential for maintaining gene silencing at heterochromatic loci. Through a live cell drug screen with genetic confirmation, we discovered that CDK9 inhibition reactivates epigenetically silenced genes in cancer, leading to restored tumor suppressor gene expression, cell differentiation, and activation of endogenous retrovirus genes. CDK9 inhibition dephosphorylates the SWI/SNF protein BRG1, which contributes to gene reactivation. By optimization through gene expression, we developed a highly selective CDK9 inhibitor (MC180295, IC50 = 5 nM) that has broad anti-cancer activity in vitro and is effective in in vivo cancer models. Additionally, CDK9 inhibition sensitizes to the immune checkpoint inhibitor ?-PD-1 in vivo, making it an excellent target for epigenetic therapy of cancer.
| S-EPMC6247954 | biostudies-literature
Project description:Cyclin-Dependent Kinase 9 (CDK9) as part of the PTEFb complex promotes transcriptional elongation by promoting RNAPII pause release. We now report that, paradoxically, CDK9 is also essential for maintaining gene silencing at heterochromatic loci. Through a live cell screen, we discovered that CDK9 inhibition reactivates epigenetically silenced genes in cancer, leading to restored tumor suppressor gene expression and cell differentiation, along with activation of endogenous retrovirus (ERV) genes. CDK9 inhibition dephosphorylates the SWI/SNF protein SMARCA4 and represses HP1α expression, both of which contribute to gene reactivation. Based on gene activation, we developed the highly selective and potent CDK9 inhibitor MC180295 (IC50 =5.1nM) that has broad anti-cancer activity in-vitro and is effective in in-vivo cancer models. Additionally, CDK9 inhibition sensitizes with the immune checkpoint inhibitor α-PD-1 in vivo, making it an excellent target for epigenetic therapy of cancer.
2020-05-26 | PXD007925 | Pride