Project description:The NuRD complex is generally thought to repress transcription at both hyper- and hypomethylated regions in the genome. In addition, the complex is involved in the DNA damage response. Here, we show that ZMYND8 bridges NuRD to a number of putative DNA-binding zinc finger proteins. The ZMYND8 MYND domain directly interacts with PPPL? motifs in the NuRD subunit GATAD2A. Furthermore, GATAD2A and GATAD2B exclusively form homodimers and they thus define mutually exclusive NuRD subcomplexes. ZMYND8 and MBD3 share a large number of genome-wide binding sites, mostly active promoters and enhancers. Depletion of ZMYND8 does not affect NuRD occupancy genome-wide and expression of NuRD/ZMYND8 target genes in steady-state asynchronous cells. However, ZMYND8 facilitates immediate recruitment of GATAD2A/NuRD to induced sites of DNA damage. These results thus show that a specific substoichiometric interaction with a NuRD subunit paralogue provides unique functionality to a distinct NuRD subcomplex.
Project description:The NuRD complex is generally thought to repress transcription at both hyper- and hypomethylated regions in the genome. In addition, the complex is involved in the DNA damage response. Here, we show that ZMYND8 bridges NuRD to a number of putative DNA-binding zinc finger proteins. The ZMYND8 MYND domain directly interacts with PPPL? motifs in the NuRD subunit GATAD2A. Furthermore, GATAD2A and GATAD2B exclusively form homodimers and they thus define mutually exclusive NuRD subcomplexes. ZMYND8 and MBD3 share a large number of genome-wide binding sites, mostly active promoters and enhancers. Depletion of ZMYND8 does not affect NuRD occupancy genome-wide and expression of NuRD/ZMYND8 target genes in steady-state asynchronous cells. However, ZMYND8 facilitates immediate recruitment of GATAD2A/NuRD to induced sites of DNA damage. These results thus show that a specific substoichiometric interaction with a NuRD subunit paralogue provides unique functionality to a distinct NuRD subcomplex.
Project description:The NuRD complex is generally thought to repress transcription at both hyper- and hypomethylated regions in the genome. In addition, the complex is involved in the DNA damage response. Here, we show that ZMYND8 bridges NuRD to a number of putative DNA-binding zinc finger proteins. The ZMYND8 MYND domain directly interacts with PPPLΦ motifs in the NuRD subunit GATAD2A. Furthermore, GATAD2A and GATAD2B exclusively form homodimers and they thus define mutually exclusive NuRD subcomplexes. ZMYND8 and MBD3 share a large number of genome-wide binding sites, mostly active promoters and enhancers. Depletion of ZMYND8 does not affect NuRD occupancy genome-wide and expression of NuRD/ZMYND8 target genes in steady-state asynchronous cells. However, ZMYND8 facilitates immediate recruitment of GATAD2A/NuRD to induced sites of DNA damage in a PAR-dependent manner. These results thus show that a specific substoichiometric interaction with a NuRD subunit paralogue provides unique functionality to a distinct NuRD subcomplex.
Project description:Upon DNA damage, histone modifications are dynamically reshaped to accommodate DNA damage signaling and repair within chromatin. In this study, we report the identification of the histone demethylase KDM5A as a key regulator of the bromodomain protein ZMYND8 and NuRD (nucleosome remodeling and histone deacetylation) complex in the DNA damage response. We observe KDM5A-dependent H3K4me3 demethylation within chromatin near DNA double-strand break (DSB) sites. Mechanistically, demethylation of H3K4me3 is required for ZMYND8-NuRD binding to chromatin and recruitment to DNA damage. Functionally, KDM5A deficiency results in impaired transcriptional silencing and repair of DSBs by homologous recombination. Thus, this study identifies a crucial function for KDM5A in demethylating H3K4 to allow ZMYND8-NuRD to operate within damaged chromatin to repair DSBs.
Project description:Mbd3, a member of nucleosome remodeling and deacetylase (NuRD) co-repressor complex, was previously identified as an inhibitor for deterministic induced pluripotent stem cell (iPSC) reprogramming, where up to 100% of donor cells successfully complete the process. NuRD can assume multiple mutually exclusive conformations, and it remains unclear whether this deterministic phenotype can be attributed to a specific Mbd3/NuRD subcomplex. Moreover, since complete ablation of Mbd3 blocks somatic cell proliferation, we aimed to explore functionally relevant alternative ways to neutralize Mbd3-dependent NuRD activity. We identify Gatad2a, a NuRD-specific subunit, whose complete deletion specifically disrupts Mbd3/NuRD repressive activity on the pluripotency circuitry during iPSC differentiation and reprogramming without ablating somatic cell proliferation. Inhibition of Gatad2a facilitates deterministic murine iPSC reprogramming within 8 days. We validate a distinct molecular axis, Gatad2a-Chd4-Mbd3, within Mbd3/NuRD as being critical for blocking reestablishment of naive pluripotency and further highlight signaling-dependent and post-translational modifications of Mbd3/NuRD that influence its interactions and assembly.
Project description:Polycomb group (PcG) proteins are involved in epigenetic silencing where they function as major determinants of cell identity, stem cell pluripotency and the epigenetic gene silencing involved in cancer development. Recently numerous PcG proteins, including CBX4, have been shown to accumulate at sites of DNA damage. However, it remains unclear whether or not CBX4 or its E3 sumo ligase activity is directly involved in the DNA damage response (DDR). Here we define a novel role for CBX4 as an early DDR protein that mediates SUMO conjugation at sites of DNA lesions. DNA damage stimulates sumoylation of BMI1 by CBX4 at lysine 88, which is required for the accumulation of BMI1 at DNA damage sites. Moreover, we establish that CBX4 recruitment to the sites of laser micro-irradiation-induced DNA damage requires PARP activity but does not require H2AX, RNF8, BMI1 nor PI-3-related kinases. The importance of CBX4 in the DDR was confirmed by the depletion of CBX4, which resulted in decreased cellular resistance to ionizing radiation. Our results reveal a direct role for CBX4 in the DDR pathway.
Project description:Many proteins that respond to DNA damage are recruited to DNA lesions. We used a proteomics approach that coupled isotopic labeling with chromatin fractionation and mass spectrometry to uncover proteins that associate with damaged DNA, many of which are involved in DNA repair or nucleolar function. We show that polycomb group members are recruited by poly(ADP ribose) polymerase (PARP) to DNA lesions following UV laser microirradiation. Loss of polycomb components results in IR sensitivity of mammalian cells and Caenorhabditis elegans. PARP also recruits two components of the repressive nucleosome remodeling and deacetylase (NuRD) complex, chromodomain helicase DNA-binding protein 4 (CHD4) and metastasis associated 1 (MTA1), to DNA lesions. PARP plays a role in removing nascent RNA and elongating RNA polymerase II from sites of DNA damage. We propose that PARP sets up a transient repressive chromatin structure at sites of DNA damage to block transcription and facilitate DNA repair.
Project description:Recent observations of RNA interference (RNAi) in the nuclei of human cells raise key questions about the extent to which nuclear and cytoplasmic RNAi pathways are shared. By directly visualizing the localization of small interfering RNA (siRNA) in live human cells, we show here that siRNA either selectively localizes in the cytoplasm or translocates into the nucleus, depending on where the silencing target RNA resides. Two siRNAs that target the small nuclear 7SK and U6 RNAs localize into the nucleus as duplexes. In contrast, an siRNA targeting the cytoplasmic hepatitis C virus replicon RNA dissociates, and only antisense strand distributes in the cytoplasm of the cells harboring the target RNA, whereas sense strand gets degraded. At the same time, both strands of the latter siRNA are distributed throughout the cytoplasm and nucleus in cells lacking the silencing target RNA. These results suggest the existence of a mechanism by which the RNAi machinery orchestrates a target-determined localization of the siRNA and the corresponding RNAi activity, and also provide evidence for formation of nuclear-programmed active RNA induced silencing complexes directly in the nucleus.
Project description:Arginine methylation is a post-translational modification required for the maintenance of genomic integrity. Cells deficient in protein arginine methyltransferase 1 (PRMT1) have DNA damage signaling defects, defective checkpoint activation and extensive genomic instability. Herein we identify the DNA damage protein and RNA binding protein, hnRNPUL1, to be a substrate of PRMT1. We identify the dimethylation of R584, R618, R620, R645, and R656, as well as the monomethylation of R661 R685 and R690 within hnRNPUL1 in U2OS cells by mass spectrometry. Moreover, we define the arginines within the RGG/RG motifs as the site of methylation by PRMT1 both in vitro and in vivo. The arginines 612, 618, 620, 639, 645, 656 and 661 within the human hnRNPUL1 RGG/RG motifs were substituted with lysines to generate hnRNPUL1(RK). hnRNPUL1(RK) was hypomethylated and lacked the ability to interact with PRMT1, unlike wild type hnRNPUL1. Co-immunoprecipitation studies showed that hnRNPUL1(RK) had impaired ability to associate with the DNA damage protein NBS1. Moreover, hnRNPUL1(RK) was not recruited to sites of DNA damage, unlike wild type hnRNPUL1, in the presence of transcriptional inhibitors. These findings define a role for arginine methylation during the DNA damage response to regulate protein-protein interactions for the recruitment at sites of damage.