Project description:Half of all human transcription factors use C2H2 zinc finger domains to specify site-specific DNA binding and yet very little is known about their role in gene regulation. Based on in vitro studies, a zinc finger code has been developed that predicts a binding motif for a particular zinc finger factor (ZNF). However, very few studies have performed genome-wide analyses of ZNF binding patterns and thus it is not clear if the binding code developed in vitro will be useful for identifying target genes of a particular ZNF. We performed genome-wide ChIP-seq for ZNF263, a C2H2 ZNF that contains 9 finger domains, a KRAB repression domain, and a SCAN domain and identified more than 5000 binding sites in K562 cells. Our results suggest that ZNF263 binds to a 24 nt site which differs from the motif predicted by the zinc finger code in several positions. Interestingly, many of the ZNF263 binding sites are located within the transcribed region of the target gene. Although ZNFs containing a KRAB domain are thought to function mainly as transcriptional repressors, many of the ZNF263 target genes are expressed at high levels. To address the biological role of ZNF263, we identified genes whose expression was altered by treatment of cells with ZNF263-specific siRNAs. Our results suggest that ZNF263 can have both positive and negative effects on transcriptional regulation of its target genes. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Examination of ZNF263 ChIP-seq in K562 cells.
Project description:The PRDM9 protein determines sites of meiotic recombination in humans by directing meiotic DNA double strand breaks to specific loci. Targeting specificity is encoded by a long array of C2H2 zinc fingers that binds to DNA. This zinc finger array is hypervariable, resulting in innumerable alleles, each with a potentially different DNA binding preference. Assessment of PRDM9 diversity is important for understanding the complexity of human population genetics, inheritance linkage patterns, and the predisposition to genetic disease. Due to the repetitive nature of the PRDM9 zinc finger array, large-scale sequencing of human PRDM9 is challenging. We therefore developed a long-read sequencing strategy to infer the diploid PRDM9 zinc finger array genotype in a high-throughput manner. From an unbiased study of PRDM9 allelic diversity in 716 individuals from 7 human populations, we detected 70 high-confidence PRDM9 alleles. Several alleles differ in frequency among human populations and 33 alleles had not been identified by previous studies, which were heavily biased to European populations. PRDM9 alleles are distinguished by their DNA binding site preferences and fall into two major categories related to the most common PRDM9-A and PRDM9-C alleles. We also find that inter-conversion between allele types is likely rare. By mapping meiotic DSBs in testis, we find that small variations in PRDM9 can substantially alter the meiotic recombination landscape, demonstrating that minor PRDM9 variants may play an under-appreciated role in shaping patterns of human recombination. In summary, our data greatly expands our knowledge of PRDM9 diversity in humans.
Project description:Half of all human transcription factors use C2H2 zinc finger domains to specify site-specific DNA binding and yet very little is known about their role in gene regulation. Based on in vitro studies, a zinc finger code has been developed that predicts a binding motif for a particular zinc finger factor (ZNF). However, very few studies have performed genome-wide analyses of ZNF binding patterns and thus it is not clear if the binding code developed in vitro will be useful for identifying target genes of a particular ZNF. We performed genome-wide ChIP-seq for ZNF263, a C2H2 ZNF that contains 9 finger domains, a KRAB repression domain, and a SCAN domain and identified more than 5000 binding sites in K562 cells. Our results suggest that ZNF263 binds to a 24 nt site which differs from the motif predicted by the zinc finger code in several positions. Interestingly, many of the ZNF263 binding sites are located within the transcribed region of the target gene. Although ZNFs containing a KRAB domain are thought to function mainly as transcriptional repressors, many of the ZNF263 target genes are expressed at high levels. To address the biological role of ZNF263, we identified genes whose expression was altered by treatment of cells with ZNF263-specific siRNAs. Our results suggest that ZNF263 can have both positive and negative effects on transcriptional regulation of its target genes. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf
Project description:The C2H2 zinc finger is the most prevalent DNA-binding motif in the mammalian proteome, with DNA-binding domains usually containing more tandem fingers than are needed for stable sequence-specific DNA recognition. To examine the reason for the frequent presence of multiple zinc fingers, we generated mice lacking finger 1 or finger 4 of the 4-finger DNA-binding domain of Ikaros, a critical regulator of lymphopoiesis and leukemogenesis. Each mutant strain exhibited a specific subset of the phenotypes observed with Ikaros null mice. Of particular relevance, fingers 1 and 4 contributed to distinct stages of B- and T-cell development and finger 4 was selectively required for tumor suppression in thymocytes and in a new model of BCR-ABL+ acute lymphoblastic leukemia. These results, combined with transcriptome profiling (this GEO submission: RNA-Seg of whole thymus from wt and the two ZnF mutants), reveal that different subsets of fingers within multi-finger transcription factors can regulate distinct target genes and biological functions, and they demonstrate that selective mutagenesis can facilitate efforts to elucidate the functions and mechanisms of action of this prevalent class of factors. Ikaros ChIP-Seq from Whole Thymus comparing wt, Ikaros-ZnF1-/- mutant and Ikaros-ZnF4-/- mutant
Project description:PRDM9 is a histone methyltransferase expressed in meiotic germ cells that determines the location of genetic recombination hotspots through binding of its allele-specific DNA binding domain. Here we characterize the genome-wide chromatin modification for two human PRDM9 alleles (A and C) in human cell lines. HEK293 cells were transfected with both alleles and an empty vector control. Resulting chromatin was subjected to H3K4me3 ChIP followed by high-throughput sequencing. We find that different PRDM9 allele largely modified chromatin in entirely different genomic regions in somatic cells determined by the protein's zinc-finger DNA binding domains. Many of the allele-specific peaks overlap sites of meiotic double-strand breaks found in vivo in human germ cells suggesting that transient expression of PRDM9 in somatic cells can reflect binding in vivo. Identify PRDM9-dependent H3K4me3 sites by comparing modified chromatin after expression of different human PRDM9 alleles in HEK293 cells.
Project description:Half of all human transcription factors use C2H2 zinc finger domains to specify site-specific DNA binding and yet very little is known about their role in gene regulation. Based on in vitro studies, a zinc finger code has been developed that predicts a binding motif for a particular zinc finger factor (ZNF). However, very few studies have performed genome-wide analyses of ZNF binding patterns and thus it is not clear if the binding code developed in vitro will be useful for identifying target genes of a particular ZNF. We performed genome-wide ChIP-seq for ZNF263, a C2H2 ZNF that contains 9 finger domains, a KRAB repression domain, and a SCAN domain and identified more than 5000 binding sites in K562 cells. Our results suggest that ZNF263 binds to a 24 nt site which differs from the motif predicted by the zinc finger code in several positions. Interestingly, many of the ZNF263 binding sites are located within the transcribed region of the target gene. Although ZNFs containing a KRAB domain are thought to function mainly as transcriptional repressors, many of the ZNF263 target genes are expressed at high levels. To address the biological role of ZNF263, we identified genes whose expression was altered by treatment of cells with ZNF263-specific siRNAs. Our results suggest that ZNF263 can have both positive and negative effects on transcriptional regulation of its target genes.
Project description:We report a novel technique, Affinity-seq, that for the first time identifies both the genome-wide binding sites of DNA-binding proteins and quantitates their relative affinities. We have applied this in vitro technique to PRDM9, the zinc-finger protein that activates genetic recombination, obtaining new information on the regulation of hotspots, whose locations and activities determine the recombination landscape. We identified 31,770 binding sites in the mouse genome for the PRDM9Dom2 variant. Comparing these results with hotspot usage in vivo, we find that less than half of potential PRDM9 binding sites are utilized in vivo. We show that hotspot usage is increased in actively transcribed genes and decreased in genomic regions containing H3K9me2/3 histone marks or bound to the nuclear lamina. These results show that a major factor determining whether a binding site will become an active hotspot and what its activity will be are constraints imposed by prior chromatin modifications on the ability of PRDM9 to bind to DNA in vivo. These constraints lead to the presence of long genomic regions depleted of recombination. The terminal zinc finger domain of PRDM9Dom2 (PRDM9ΔZnF1Dom2, 412–847 aa), the allele present in C57BL/6J (B6) mice was cloned and tagged with 6His-HALO and then expressed in E. coli. DNA sheared to 180–200 bp is provided in considerable excess to provide competition between DNA binding sites. Following binding, DNA–protein complexes are then isolated on streptavidin beads and the DNA extracted for deep sequencing. Two replicate Affinity-seq samples were sequenced at 100-bp reads using the Illumina HiSeq 2500. Alignments to the mm9 mouse genome were obtained utilizing BWA v1.2.3 with default parameters and reads which failed to align to unique positions in the genome were discarded. Peaks were called individually for the two replicates with MACS2 at a p value threshold of 0.01 utilizing a control dataset obtained by sequencing the input DNA and subsequently compared, leading ultimately to combining the two replicates for definitive analysis.
Project description:The largest and most diverse class of eukaryotic transcription factors contain Cys2-His2 zinc fingers (C2H2-ZFs), each of which typically binds a DNA nucleotide triplet within a larger binding site. Frequent recombination and diversification of their DNA-contacting residues suggests that these zinc fingers play a prevalent role in adaptive evolution. Very little is known about the function and evolution of the vast majority of C2H2-ZFs, including whether they even bind DNA. Using the bacterial 1-hybrid (B1H) system, we determined DNA-binding motifs for thousands of individual natural C2H2-ZFs, and correlated them with C2H2-ZF specificity residues. The data reported here includes results of protein-binding microarray (PBM) assays for 146 of these natural C2H2-ZFs, performed in order to validate B1H assays and to explore the DNA-binding specificity of C2H2-ZFs. Protein binding microarray (PBM) experiments were performed for a set of 185 variants of mouse Egr1 in which the third zinc finger was replaced by different C2H2-ZFs from different organisms. Briefly, the PBMs involved binding GST-tagged DNA-binding proteins to two double-stranded 44K Agilent microarrays, each containing a different DeBruijn sequence design, in order to determine their sequence preferences. Details of the PBM protocol are described in Berger et al., Nature Biotechnology 2006. Among the 185 variants examined, 146 variants yielded motifs in PBMs, which are included here.
Project description:Meiotic crossovers result from homology-directed repair of double strand breaks (DSBs). Unlike yeast and plants, where DSBs are generated near gene promoters, in many vertebrates, DSBs are enriched at hotspots determined by the DNA binding activity of the rapidly evolving zinc finger array of PRDM9 (PR domain zinc finger protein 9), which subsequently catalyzes trimethylation of lysine 4 and lysine 36 of Histone H3 in nearby nucleosomes. Here, we identify the dual histone methylation reader ZCWPW1, which is tightly co-expressed during spermatogenesis with Prdm9 and co-evolved with Prdm9 in vertebrates, as an essential meiotic recombination factor required for efficient synapsis and repair of PRDM9-dependent DSBs. In sum, our results indicate that the evolution of dual histone methylation reader/writer system involving Prdm9 and Zcwpw1 facilitated a shift in genetic recombination away from a static pattern near genes towards a flexible pattern controlled by the rapidly evolving DNA binding activity of PRDM9