Dual DNA demethylation mechanisms implement epigenetic memory driven by the pioneer factor PAX7 [RNA-seq]
Ontology highlight
ABSTRACT: Pioneer transcription factors have the unique ability to open chromatin at enhancers to implement new cell fates. They also provide epigenetic memory through demethylation of enhancer DNA but the underlying mechanisms remain unclear. We now show that the pioneer PAX7 triggers DNA demethylation using two replication-dependent mechanisms, including direct PAX7 interaction with the UHRF1-DNMT1 complex that is responsible for DNA methylation maintenance. PAX7 binds to UHRF1 and prevents its interaction with DNMT1, thus blocking activation of its enzyme activity. The TET DNA demethylases also contribute to the replication-dependent loss of DNA methylation. Thus, PAX7 hijacks UHRF1 to block activation of DNMT1 after replication leading to loss of DNA methylation by dilution and the process is accelerated by the action of TET demethylases.
Project description:Pioneer transcription factors have the unique ability to open chromatin at enhancers to implement new cell fates. They also provide epigenetic memory through demethylation of enhancer DNA but the underlying mechanisms remain unclear. We now show that the pioneer PAX7 triggers DNA demethylation using two replication-dependent mechanisms, including direct PAX7 interaction with the UHRF1-DNMT1 complex that is responsible for DNA methylation maintenance. PAX7 binds to UHRF1 and prevents its interaction with DNMT1, thus blocking activation of its enzyme activity. The TET DNA demethylases also contribute to the replication-dependent loss of DNA methylation. Thus, PAX7 hijacks UHRF1 to block activation of DNMT1 after replication leading to loss of DNA methylation by dilution and the process is accelerated by the action of TET demethylases.
Project description:Pioneer transcription factors have the unique ability to open chromatin at enhancers to implement new cell fates. They also provide epigenetic memory through demethylation of enhancer DNA but the underlying mechanisms remain unclear. We now show that the pioneer PAX7 triggers DNA demethylation using two replication-dependent mechanisms, including direct PAX7 interaction with the UHRF1-DNMT1 complex that is responsible for DNA methylation maintenance. PAX7 binds to UHRF1 and prevents its interaction with DNMT1, thus blocking activation of its enzyme activity. The TET DNA demethylases also contribute to the replication-dependent loss of DNA methylation. Thus, PAX7 hijacks UHRF1 to block activation of DNMT1 after replication leading to loss of DNA methylation by dilution and the process is accelerated by the action of TET demethylases.
Project description:Pioneer transcription factors have the unique ability to open chromatin at enhancers to implement new cell fates. They also provide epigenetic memory through demethylation of enhancer DNA but the underlying mechanisms remain unclear. We now show that the pioneer PAX7 triggers DNA demethylation using two replication-dependent mechanisms, including direct PAX7 interaction with the UHRF1-DNMT1 complex that is responsible for DNA methylation maintenance. PAX7 binds to UHRF1 and prevents its interaction with DNMT1, thus blocking activation of its enzyme activity. The TET DNA demethylases also contribute to the replication-dependent loss of DNA methylation. Thus, PAX7 hijacks UHRF1 to block activation of DNMT1 after replication leading to loss of DNA methylation by dilution and the process is accelerated by the action of TET demethylases.
Project description:Pioneer transcription factors have the unique ability to open chromatin at enhancers to implement new cell fates. They also provide epigenetic memory through demethylation of enhancer DNA but the underlying mechanisms remain unclear. We now show that the pioneer PAX7 triggers DNA demethylation using two replication-dependent mechanisms, including direct PAX7 interaction with the UHRF1-DNMT1 complex that is responsible for DNA methylation maintenance. PAX7 binds to UHRF1 and prevents its interaction with DNMT1, thus blocking activation of its enzyme activity. The TET DNA demethylases also contribute to the replication-dependent loss of DNA methylation. Thus, PAX7 hijacks UHRF1 to block activation of DNMT1 after replication leading to loss of DNA methylation by dilution and the process is accelerated by the action of TET demethylases.
Project description:Genome-wide DNA demethylation is a unique feature of mammalian development and naïve pluripotent stem cells. So far, it was unclear how mammals specifically achieve global DNA hypomethylation, given the high conservation of the DNA (de-)methylation machinery among vertebrates. We found that DNA demethylation requires TET activity but mostly occurs at sites where TET proteins are not bound suggesting a rather indirect mechanism. Among the few specific genes bound and activated by TET proteins was the naïve pluripotency and germline marker Dppa3 (Pgc7, Stella), which undergoes TDG dependent demethylation. The requirement of TET proteins for genome-wide DNA demethylation could be bypassed by ectopic expression of Dppa3. We show that DPPA3 binds and displaces UHRF1 from chromatin and thereby prevents the recruitment and activation of the maintenance DNA methyltransferase DNMT1. We demonstrate that DPPA3 alone can drive global DNA demethylation when transferred to amphibians (Xenopus) and fish (medaka), both species that naturally do not have a Dppa3 gene and exhibit no post-fertilization DNA demethylation. Our results show that TET proteins are responsible for active and - indirectly also for - passive DNA demethylation; while TET proteins initiate local and gene-specific demethylation in vertebrates, the recent emergence of DPPA3 introduced a unique means of genome-wide passive demethylation in mammals and contributed to the evolution of epigenetic regulation during early mammalian development.
Project description:The multi-domain protein UHRF1 (ubiquitin-like, containing PHD and RING finger domains, 1) recruits DNMT1 for DNA methylation maintenance during DNA replication. Here, we show that MOF (Males absent On the First) is an acetyltransferase of UHRF1 to acetylate UHRF1 at Lys670 in the pre-RING linker region whereas HDAC1 is a deacetylase of UHRF1 at the same site. The MOF/HDAC1-mediated acetylation in UHRF1 is cell-cycle regulated and peaks at G1/S phase, in line with the function of UHRF1 in recruiting DNMT1 to maintain DNA methylation. In addition, UHRF1 acetylation significantly enhances its E3 ligase activity and elimination of UHRF1 acetylation at these sites attenuates UHRF1-mediated H3 ubiquitination, which in turn impairs the DNMT1 recruitment and DNA methylation. Taken together, these findings not only identify MOF as a new acetyltransferase for UHRF1 but also reveal a novel mechanism underlying the regulation of DNA methylation maintenance through MOF-mediated UHRF1 acetylation.
Project description:We have generated and validated degron alleles of UHRF1 and/or DNMT1 in several human colorectal cancer cell lines. We then used genomics and bioinformatics to precisely describe he DNA demethylation dynamics in these cells, leading to the conclusion that UHRF1 maintains DNA methylation in cancer cells not only by stimulating DNMT1. Proteomics and genetics lead us to conclude that UHRF1 regulates DNMT3A, DNMT3B and TET2 activity in addition to regulating DNMT1. The tools we have developed will be valuable for future research efforts, and our results advance our understanding of cancer epigenetics, with potentially important therapeutic applications.
Project description:Stable inheritance of DNA methylation is critical for maintaining the differentiated phenotypes in multicellular organisms. However, the molecular basis ensuring high fidelity of maintenance DNA methylation is largely unknown. Here, we demonstrate that two distinct modes of DNMT1 recruitment, one is DNA replication-coupled and the other is uncoupled mechanism, regulate the stable inheritance of DNA methylation. PCNA-associated factor 15 (PAF15) represents a primary target of UHRF1 and undergoes dual mono-ubiquitylation (PAF15Ub2) on chromatin. PAF15Ub2 specifically interacts with DNMT1 and controls the recruitment of DNMT1 in a DNA replication-coupled manner. Thus, loss of PAF15Ub2 results in impaired DNA methylation at sites replicating during early S phase. In contrast, outside of S phase or when PAF15 ubiquitylation is perturbed, UHRF1 ubiquitylates histone H3 to promote DNMT1 recruitment. Together, we identify replication-coupled and uncoupled mechanisms of maintenance DNA methylation, both of which collaboratively ensure the stable DNA methylation.
Project description:Histone H3 mono-ubiquitination, catalyzed by the RING E3 ubiquitin ligase UHRF1, is appreciated as a docking site for DNMT1 during DNA replication to facilitate DNA methylation maintenance. Its functions beyond this are unknown. Here, we identify simultaneous increases in UHRF1-dependent H3K18ub and SUV39H1/2-dependent H3K9me3 as prominent epigenetic alterations accompanying DNA hypomethylation induced by DNMT1 inhibition. Integrative epigenomics analyses reveal that transient accumulation of hemi-methylated DNA, resulting from incomplete DNA methylation maintenance, stimulates UHRF1-dependent H3K18ub at CpG islands that nucleates new domains of H3K9me3 and impedes PRC2 activity in these genomic regions. Notably, H3K18ub enhances the methyltransferase activity of SUV39H1/2, leading to increased H3K9me3 at these CpG island promoters. Blocking H3K18ub-dependent SUV39H1/2 activity enhances the efficacy of DNMT1 inhibitors. Collectively, these findings reveal a novel histone ubiquitination-methylation crosstalk mechanism that reinforces heterochromatin states in the absence of DNA methylation and proposes new strategies for improving cancer epigenetic therapy.
Project description:Accumulative studies indicate that DNA maintenance methylation by DNMT1 is initiated by binding of UHRF1 to replication fork. However, how UHRF1 gains access to chromatin in S phase is poorly understood. Here we report that LSH, a SNF2 family chromatin remodeler, facilitates DNA methylation in somatic cells primarily by promoting DNA methylation by DNMT1. We show that knockout of LSH in various somatic cells resulted in substantial reduction of DNA methylation, whereas knockout of DNMT3A and DNMT3B only moderately reduced the level of DNA methylation. Consistent with a role in maintenance methylation, genome-wide analysis of DNA methylation revealed a widespread reduction of DNA methylation in all genomic elements in LSH null cells. Mechanistically, we demonstrate that LSH interacts with UHRF1 but not DNMT1 and facilitates UHRF1 chromatin association, UHRF1-catalyzed H3 ubiquitination, and subsequent DNMT1 recruitment to replication fork. Notably, UHRF1 also enhances LSH association with replication fork. Thus, our study identifies LSH as an essential factor for maintenance methylation and provides novel insight into how LSH facilitates maintenance methylation.