Project description:Histone methylation occurs on both lysine and arginine residues and its dynamic regulation plays a critical role in chromatin biology. Here we identify the UHRF1 PHD domain (PHDUHRF1), an important regulator of DNA CpG methylation, as an unanticipated histone H3 unmodified arginine 2 (H3R2)-recognition modality. This conclusion is based on binding studies and co-crystal structures of the PHDUHRF1 bound to histone H3 peptides, where the guanidinium group of unmodified R2 forms an extensive intermolecular hydrogen bond network, with methylation of H3R2, but not H3K4 or H3K9, disrupting complex formation. We have identified direct target genes of UHRF1 from microarray and ChIP studies. Importantly, we show that UHRF1’s ability to repress its direct target gene expression is dependent on PHDUHRF1 binding to unmodified H3R2, thereby demonstrating the functional importance of this recognition event and supporting the potential for crosstalk between histone arginine methylation and UHRF1 function. UHRF1 protein was depleted in HCT116 cells by shRNA treatment. Total RNA was purified and used to determine the global gene transcription profiles by microarray assays. The UHRF1-regulated genes were identified by comparing the gene expression profiles of control and UHRF1-depleted HCT116 cells.
Project description:Histone methylation occurs on both lysine and arginine residues and its dynamic regulation plays a critical role in chromatin biology. Here we identify the UHRF1 PHD domain (PHDUHRF1), an important regulator of DNA CpG methylation, as an unanticipated histone H3 unmodified arginine 2 (H3R2)-recognition modality. This conclusion is based on binding studies and co-crystal structures of the PHDUHRF1 bound to histone H3 peptides, where the guanidinium group of unmodified R2 forms an extensive intermolecular hydrogen bond network, with methylation of H3R2, but not H3K4 or H3K9, disrupting complex formation. We have identified direct target genes of UHRF1 from microarray and ChIP studies. Importantly, we show that UHRF1’s ability to repress its direct target gene expression is dependent on PHDUHRF1 binding to unmodified H3R2, thereby demonstrating the functional importance of this recognition event and supporting the potential for crosstalk between histone arginine methylation and UHRF1 function.
Project description:The chromatin-binding E3 ubiquitin ligase Ubiquitin-like with PHD and RING finger domains 1 (UHRF1) maintains DNA methylation patterning in cancer cells through multivalent histone and DNA recognition. The tandem Tudor domain (TTD) of UHRF1 is well-characterized as a reader of lysine 9 di- and tri-methylation on histone H3 (H3K9me2/me3) and, more recently, lysine 126 di- and tri- methylation on DNA ligase 1 (LIG1K126me2/me3). However, the functional significance and selectivity of these interactions remains unclear. In this study, we used protein domain microarrays to search for additional readers of LIG1K126me2, the preferred methyl state bound by the UHRF1 TTD. We show that the UHRF1 TTD binds LIG1K126me2 with high affinity and selectivity compared to other known methyllysine readers. Notably, and unlike H3K9me2/me3, the UHRF1 plant homeodomain (PHD) and its N-terminal linker (L2) do not contribute to multivalent LIG1K126me2 recognition along with the TTD. To test the functional significance of this interaction, we designed a LIG1K126me2 cell-penetrating peptide (CPP). Consistent with LIG1 knockdown in somatic cells, uptake of the CPP had no effect on the DNA methylation maintenance function of UHRF1. Further, we did not detect changes in bulk DNA methylation after chemical or genetic disruption of lysine methyltransferase activity. Collectively, these studies identify UHRF1 as a selective reader of LIG1K126me2 in vitro, implicate the UHRF1 TTD as a dispensable domain for DNA methylation maintenance, and call into question existing models of methyllysine-dependent DNA methylation maintenance in somatic cancer cells.
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:Plant Homeo Domain (PHD) is a versatile chromatin reader/effector module which recognizes methylated, acetylated or unmodified histone substrates and regulates cellular gene expression programs. Although PHD domains shows selective epigenetic recognition of methylated, acetylated and unmodified histone substrates, there has been no previous report on its catalytic function regulating malignant transformation of cells. Here we report that PHD finger of UBR7 (Ubiquitin Protein Ligase E3 Component N-Recognin 7 (Putative)), in isolation or in context of full length protein, harbors E3 ubiquitin ligase activity towards monoubiquitination of histone H2B at lysine 120 . Knockdown of UBR7 in MCF10a and breast cancer cells decreased H2BK120ub both at the global levels and on specific genes. Conversely, overexpression of wild type, but not catalytic mutant, rescued H2BK120ub levels. Low UBR7 expression was associated with basal-like and triple negative breast cancers as well as showed poor expression in metastatic tumors. Consistently, UBR7 loss resulted in invasion properties, induced epithelial-to-mesenchymal transition and promoted metastasis. Conversely, ectopic expression of UBR7 reduced cell growth, invasion and tumor growth in mouse fat pad. Mechanistically, UBR7 reduced H2BK120ub gene body of cell-adhesion related genes as well as gene expression including on CDH4 gene. Importantly, rebuilding CDH4 levels rescued invasion phenotypes seen in UBR7-low cells. Collectively, our results establish that UBR7 PHD has novel H2B ubiquitin ligase activity and it suppresses tumor growth in basal-like breast cancers.
Project description:Plant Homeo Domain (PHD) is a versatile chromatin reader/effector module which recognizes methylated, acetylated or unmodified histone substrates and regulates cellular gene expression programs. Although PHD domains shows selective epigenetic recognition of methylated, acetylated and unmodified histone substrates, there has been no previous report on its catalytic function regulating malignant transformation of cells. Here we report that PHD finger of UBR7 (Ubiquitin Protein Ligase E3 Component N-Recognin 7 (Putative)), in isolation or in context of full length protein, harbors E3 ubiquitin ligase activity towards monoubiquitination of histone H2B at lysine 120 . Knockdown of UBR7 in MCF10a and breast cancer cells decreased H2BK120ub both at the global levels and on specific genes. Conversely, overexpression of wild type, but not catalytic mutant, rescued H2BK120ub levels. Low UBR7 expression was associated with basal-like and triple negative breast cancers as well as showed poor expression in metastatic tumors. Consistently, UBR7 loss resulted in invasion properties, induced epithelial-to-mesenchymal transition and promoted metastasis. Conversely, ectopic expression of UBR7 reduced cell growth, invasion and tumor growth in mouse fat pad. Mechanistically, UBR7 reduced H2BK120ub gene body of cell-adhesion related genes as well as gene expression including on CDH4 gene. Importantly, rebuilding CDH4 levels rescued invasion phenotypes seen in UBR7-low cells. Collectively, our results establish that UBR7 PHD has novel H2B ubiquitin ligase activity and it suppresses tumor growth in basal-like breast cancers.
Project description:UHRF1 (ubiquitin-like with PHD and ring finger domains 1) is an epigenetic regulator that is involved in the regulation of DNA and histone methylation and many other cellular events. The UHRF1 is frequently found to be overexpressed in various human cancers including retinoblastoma, and its overexpression has been associated with tumor-promoting effects such as inhibition of apoptosis and high metastatic potential. However, the detailed mechanisms underlying these tumor-promoting functions of UHRF1 in retinoblastoma still remain unclear. In this study, we uncovered that UHRF1 depletion in retinoblastoma cells sensitizes the cells to histone deacetylase (HDAC) inhibitors, augmenting apoptotic cell death. To understand the molecular mechanisms underlying the enhanced sensitivity to HDAC inhibitors in the UHRF1-depleted retinoblastoma cells, we performed the gene expression profiling in UHRF1-knockdown Y79 cells in comparison with control-knockdown cells by RNA-sequencing to identify differentially expressed genes. Our RNA-seq results revealed that UHRF1 depletion downregulates redox-responsive genes such as GSTA4 and TXN2, leading to increased intracellular oxidative stress and higher susceptibility to HDAC inhibitor treatment.
Project description:Posttranslational modifications of histone N-terminal tails influence the status of chromatin and eventually control the transcriptional outcome of a particular gene. As a histone H3K9 methyltransferase (HMTase) in higher eukaryotes, G9a-mediated transcriptional repression is the major epigenetic silencing machinery. UHRF1 (ubiquitin-like with PHD and ring finger domains I) binds to hemi-methylated DNA and plays essential role in maintenance of DNA methylation by recruiting DNMT1. Here, we provide evidence that UHRF1 is transcriptionally downregulated by H3K9 HMTase G9a. We found that increased expression of G9a along with transcription factor YY1 specifically represses UHRF1 transcription. We uncovered showed that G9a regulates UHRF1-mediated H3K23 ubiquitylation and proper DNA replication maintenance by FACS analysis and propose that H3K9 HMTase G9a is a specific epigenetic regulator of UHRF1.
Project description:DNA methylation is an essential epigenetic mark in mammals. It controls gene expression and genome stability. Global DNA methylation pattern is abnormal in cancers. Ubiquitin like with PHD and RING finger domains 1 (UHRF1) is a key epigenetic regulator that recruits and activates DNA methyltransferase 1 (DNMT1), the methylation maintenance enzyme. UHRF1 is a proven oncogene and its overexpression transforms cells in vitro and causes cancer in animal models. Therefore, UHRF1 provides a unique entry point into the links between epigenetics and cancer. However, it is still not fully clear how UHRF1 works in cancer cells. To understand UHRF1 functions in cancer, we employed experimental strategy to use an advanced chemical/genetic system, the auxin-inducible degron (AID) technology, whereby the degron-fused protein can be totally and rapidly degraded upon the addition of a small molecule, auxin. We chose the human CRC cell line HCT116 as our model and successfully generated UHRF1-AID and DNMT1-AID. Through this study, we made the significant discovery that UHRF1 not only regulates DNMT1, but also influences the activities of de novo methyltransferases DNMT3A and DNMT3B, as well as the active demethylase TET2.
Project description:DNA methylation is an essential epigenetic mark in mammals. It controls gene expression and genome stability. Global DNA methylation pattern is abnormal in cancers. Ubiquitin like with PHD and RING finger domains 1 (UHRF1) is a key epigenetic regulator that recruits and activates DNA methyltransferase 1 (DNMT1), the methylation maintenance enzyme. UHRF1 is a proven oncogene and its overexpression transforms cells in vitro and causes cancer in animal models. Therefore, UHRF1 provides a unique entry point into the links between epigenetics and cancer. However, it is still not fully clear how UHRF1 works in cancer cells. To understand UHRF1 functions in cancer, we employed experimental strategy to use an advanced chemical/genetic system, the auxin-inducible degron (AID) technology, whereby the degron-fused protein can be totally and rapidly degraded upon the addition of a small molecule, auxin. We chose the human CRC cell line HCT116 as our model and successfully generated UHRF1-AID and DNMT1-AID. Through this study, we made the significant discovery that UHRF1 not only regulates DNMT1, but also influences the activities of de novo methyltransferases DNMT3A and DNMT3B, as well as the active demethylase TET2.