Project description:SETMAR/Metnase is a naturally occurring fusion protein that consists of a histone-lysine methyltransferase domain and an HsMar1 transposase. To elucidate the biological role of SETMAR, it is crucial to identify genomic targets to which SETMAR specifically binds and link these sites to the regulation of gene expression. Herein, we mapped the genomic landscape of SETMAR in a near-haploid human leukemia cell line (HAP1) in order to identify on-target and off-target binding sites at high resolution and to elucidate their role in terms of gene expression. Our analysis revealed a perfect correlation between SETMAR and inverted tandem repeats (ITRs) of HsMar1 transposon remnants, which are considered as natural target sites for SETMAR chromosome binding. However, we did not detect any untargeted events at non-ITR sequences, calling into question previously proposed off-target binding sites. We identified sequence fidelity of the ITR motif as a key factor for determining the binding affinity of SETMAR for chromosomes, as higher ITR fidelity resulted in increased affinity for chromatin and stronger repression of SETMAR-bound gene loci. These associations highlight how SETMAR’s chromatin binding fine-tune gene regulatory networks in human tumour cells.
Project description:SILAC labeled HT-1080 cell lysate (K0R0 and K8R10) were treated with active or catalytic inactive SETMAR methyltransferase enzyme. Samples were combined and proteins modified by methyl-lysine enriched by 3xMBT. Quantitative comparison identified candidate proteins with increase methylation following incubation with SETMAR.
Project description:Approximately 50 million years ago, the Hsmar1 transposon entered the primate lineage giving rise to a new protein, a chimeric fusion of a SET domain and the Hsmar1 transposase. This protein, SETMAR or Metnase, is broadly expressed in human tissues and has been shown to retain its ancestral sequence-specific binding to Hsmar1 terminal inverted repeat (TIR) sequences found at the ends of the transposons. Despite the fact that there were estimated to be anywhere from 1500-7000 TIR sites within the human genome, the relevance of SETMAR-TIR interactions was unknown. Here, we report the crystal structure of the SETMAR DNA-binding domain (DBD) complexed with TIR DNA at 2.37 Å. The DBD structure includes two helix-turn-helix motifs (HTH1 and HTH2), which dimerize through HTH1, and confer sequence-specific recognition of the TIR through nucleobase-specific interactions with R371 in HTH1 and R417, H427, S428, and R432 in HTH2. The extent of genome-wide binding was determined by chromatin immunoprecipitation sequencing (ChIP-seq) analysis yielding a total of 7457 SETMAR bound sites. The effect of SETMAR on the transcriptome was assessed by RNA-seq analysis; among the 177 differentially regulated transcripts, a cluster of histones on chromosome 6 were found to be repressed. The dimeric SETMAR structure with each DBD bound to TIR DNA, the presence of eleven TIR sites within the histone gene cluster, and previously reported DNA looping activity are consistent with a direct regulatory mechanism in which SETMAR represses mRNA expression for specific genes through chromatin looping.
Project description:Approximately 50 million years ago, the Hsmar1 transposon entered the primate lineage giving rise to a new protein, a chimeric fusion of a SET domain and the Hsmar1 transposase. This protein, SETMAR or Metnase, is broadly expressed in human tissues and has been shown to retain its ancestral sequence-specific binding to Hsmar1 terminal inverted repeat (TIR) sequences found at the ends of the transposons. Despite the fact that there were estimated to be anywhere from 1500-7000 TIR sites within the human genome, the relevance of SETMAR-TIR interactions was unknown. Here, we report the crystal structure of the SETMAR DNA-binding domain (DBD) complexed with TIR DNA at 2.37 Å. The DBD structure includes two helix-turn-helix motifs (HTH1 and HTH2), which dimerize through HTH1, and confer sequence-specific recognition of the TIR through nucleobase-specific interactions with R371 in HTH1 and R417, H427, S428, and R432 in HTH2. The extent of genome-wide binding was determined by chromatin immunoprecipitation sequencing (ChIP-seq) analysis yielding a total of 7457 SETMAR bound sites. The effect of SETMAR on the transcriptome was assessed by RNA-seq analysis; among the 177 differentially regulated transcripts, a cluster of histones on chromosome 6 were found to be repressed. The dimeric SETMAR structure with each DBD bound to TIR DNA, the presence of eleven TIR sites within the histone gene cluster, and previously reported DNA looping activity are consistent with a direct regulatory mechanism in which SETMAR represses mRNA expression for specific genes through chromatin looping.
Project description:Transposons impart dynamism to the genomes they inhabit and their movements frequently rewire the control of nearby genes. Occasionally, their proteins are domesticated when they evolve a new function. SETMAR is a protein methylase with a sequence-specific DNA binding domain. It began to evolve about 50 million years ago when an Hsmar1 transposon integrated downstream of a SET-domain methylase gene. Here we show that the DNA-binding domain of the transposase targets the enzyme to transposon-end remnants and that this is capable of regulating gene expression, dependent on the methylase activity. When SETMAR was modestly overexpressed in human cells, almost 1500 genes changed expression by more than 2-fold (65% up- and 35% down-regulated). These genes were enriched for the KEGG Pathways in Cancer and include several transcription factors important for development and differentiation. Expression of a similar level of a methylase-deficient SETMAR changed the expression of many fewer genes, 77% of which were down-regulated with no significant enrichment of KEGG Pathways. Our data is consistent with a model in which SETMAR is part of an anthropoid primate-specific regulatory network centered on the subset of genes containing a transposon end.
Project description:SIN3 associates with RPD3 and other accessory proteins to form the SIN3 histone modifying complex. A single Sin3A gene encodes multiple SIN3 isoforms, of which SIN3 187 and SIN3 220 are predominant. Previous studies from our laboratory and others have indicated that SIN3 isoforms play non-redundant roles during fly development, however, the genes regulated by SIN3 isoforms are not known. We mapped the genome-wide binding sites of SIN3 isoforms in Drosophila. We established stable S2 cell lines that express either HA-tagged SIN3 187 or SIN3 220. The binding profiles revealed that the majority of the binding sites of SIN3 isoforms are overlapping. Our data revealed that SIN3 isoforms localize to euchromatic regions of the genome and enrichment of SIN3 isoforms are generally concentrated around the transcription start sites of genes. In addition, the extent of SIN3 binding confirmed previous findings indicating that SIN3 is a global transcriptional regulator. Genome-wide binding analysis of SIN3 187 and SIN3 220 in Drosophila. Using chromatin prepared from cell lines expressing either of the isoforms, we performed chromatin immunoprecipitation on chromatin prepared from cells that expresses either of the isoforms using an antibody against HA (ChIP). We coupled our ChIP with high resolution deep sequencing (ChIP-seq) to identify genomic targets of SIN3 isoforms.
Project description:Aberrant expression of SOX9 in human colorectal cancer cells suggests its roles in the development of colorectal cancer. To gain insight into SOX9-mediated transcriptional regulation in colorectal cancer cells, we attempted to identify its physiological targets on a genome-scale using chromatin immunoprecipitation (ChIP) followed by sequencing (ChIP-seq) in HT-29, human colorectal cancer cells.