ABSTRACT: Analysis of transcription start sites from nascent RNA identifies a unified architecture of initiation at mammalian promoters and enhancers (GRO-seq)
Project description:Analysis of transcription start sites from nascent RNA identifies a unified architecture of initiation at mammalian promoters and enhancers (GRO-cap)
| PRJNA258295 | ENA
Project description:Analysis of transcription start sites from nascent RNA identifies a unified architecture of initiation at mammalian promoters and enhancers
Project description:Analysis of transcription start sites from nascent RNA identifies a unified architecture of initiation at mammalian promoters and enhancers (PRO-seq)
Project description:Despite the conventional distinction between promoters and enhancers, they share many features in mammals, including divergent transcription and similar modes of transcription factor (TF) binding. Here, we examine the architecture of transcription initiation genome-wide through comprehensive mapping of transcription start sites (TSSs) in human lymphoblastoid B-cell (GM12878) and chronic myelogenous leukemic (K562) tier 1, ENCODE cell lines using a nuclear run-on protocol called GRO-cap. This method captures TSSs for both stable and unstable transcripts, thus allowing us to conduct detailed comparisons between thousands of promoters and enhancers in human cells. These analyses reveal a common architecture of initiation at both promoters and enhancers, including tightly spaced (110 bp) divergent initiation that features similar frequencies of core-promoter sequence elements, highly-positioned flanking nucleosomes, and two modes of TF binding. Transcript elongation stability, a feature determined after transcription initiation, provides a more fundamental distinction between promoters and enhancers than the relative abundance of histone modifications and the presence of TFs or coactivators. These results support a unified model of transcription initiation at both promoters and enhancers.
Project description:Despite the conventional distinction between promoters and enhancers, they share many features in mammals, including divergent transcription and similar modes of transcription factor (TF) binding. Here, we examine the architecture of transcription initiation genome-wide through comprehensive mapping of transcription start sites (TSSs) in human lymphoblastoid B-cell (GM12878) and chronic myelogenous leukemic (K562) tier 1, ENCODE cell lines using a nuclear run-on protocol called GRO-cap. This method captures TSSs for both stable and unstable transcripts, thus allowing us to conduct detailed comparisons between thousands of promoters and enhancers in human cells. These analyses reveal a common architecture of initiation at both promoters and enhancers, including tightly spaced (110 bp) divergent initiation that features similar frequencies of core-promoter sequence elements, highly-positioned flanking nucleosomes, and two modes of TF binding. Transcript elongation stability, a feature determined after transcription initiation, provides a more fundamental distinction between promoters and enhancers than the relative abundance of histone modifications and the presence of TFs or coactivators. These results support a unified model of transcription initiation at both promoters and enhancers.
Project description:Despite the conventional distinction between promoters and enhancers, they share many features in mammals, including divergent transcription and similar modes of transcription factor (TF) binding. Here, we examine the architecture of transcription initiation genome-wide through comprehensive mapping of transcription start sites (TSSs) in human lymphoblastoid B-cell (GM12878) and chronic myelogenous leukemic (K562) tier 1, ENCODE cell lines using a nuclear run-on protocol called GRO-cap. This method captures TSSs for both stable and unstable transcripts, thus allowing us to conduct detailed comparisons between thousands of promoters and enhancers in human cells. These analyses reveal a common architecture of initiation at both promoters and enhancers, including tightly spaced (110 bp) divergent initiation that features similar frequencies of core-promoter sequence elements, highly-positioned flanking nucleosomes, and two modes of TF binding. Transcript elongation stability, a feature determined after transcription initiation, provides a more fundamental distinction between promoters and enhancers than the relative abundance of histone modifications and the presence of TFs or coactivators. These results support a unified model of transcription initiation at both promoters and enhancers.
Project description:Divergent transcription, in which reverse-oriented transcripts occur upstream of eukaryotic promoters in regions devoid of annotated genes, has been suggested to be a general property of active promoters. Here we show that the human basal RNA polymerase II transcriptional machinery and core promoter are inherently unidirectional, and that reverse-oriented transcripts originate from their own cognate reverse-directed core promoters. In vitro transcription analysis and mapping of nascent transcripts in cells revealed that core promoters are unidirectional and that sequences at reverse start sites are similar to those of their forward counterparts. The use of DNase I accessibility to define proximal promoter borders revealed that about half of promoters are unidirectional and that these unidirectional promoters are depleted at their upstream edges of reverse core promoter sequences and their associated chromatin features. Divergent transcription is thus not an inherent property of the transcription process, but rather the consequence of the presence of both forward- and reverse-directed core promoters. Using 5'-GRO-seq and GRO-seq to determine mechanisms of divergent transcription initiation
Project description:Rev-Erba and Rev-Erbb are nuclear receptors that regulate the expression of genes involved in the control of circadian rhythm, metabolism, and inflammatory responses. Rev-Erbs function as transcriptional repressors by recruiting NCoR/HDAC3 co-repressor complexes to Rev-Erb response elements in enhancers and promoters of target genes, but the molecular basis for cell-specific programs of repression is not known. Here, we present evidence that in macrophages, Rev-Erbs regulate target gene expression by inhibiting the functions of distal enhancers that are selected by macrophage lineage-determining factors, thereby establishing a macrophage-specific program of repression. Remarkably, the repressive functions of Rev-Erbs are associated with their ability to inhibit the transcription of enhancer-derived RNAs (eRNAs). Furthermore, targeted degradation of eRNAs at two enhancers subject to negative regulation by Rev-Erbs resulted in reduced expression of nearby mRNAs, implying a direct role of these eRNAs in enhancer function. By precisely defining eRNA start sites using a method that quantifies nascent 5' ends (5'-GRO-Seq), we show that transfer of full enhancer activity to a target promoter requires both the sequences mediating transcription factor binding and the specific sequences encoding the eRNA transcript. These studies provide evidence for direct roles of eRNAs in contributing to enhancer functions and suggest that Rev-Erbs act to suppress gene expression at a distance by repressing eRNA transcription. Using ChIPseq, GRO-seq, and 5'GRO-seq to determine mechanism of RevErb in transcriptional regulation in macrophages
Project description:Antisense transcription is common at mammalian promoters. Previous studies have largely focused on characterizing antisense transcription initiating upstream of gene transcription start sites. Here, we systematically characterize promoter-proximal antisense transcription downstream of gene transcription starts sites in human T-47D cells, investigating the genomic context of downstream antisense transcription. We find that downstream antisense transcription is widespread, with antisense transcription initiation observed within 2 kb of 28% of gene transcription start sites. Downstream antisense transcription is correlated with many regulatory features at gene promoters despite not being categorically associated with gene activation or repression. At the downstream antisense transcription start site, DNA is accessible, is enriched for protein-associated sequences motifs, and is bound by a variety of transcription factors. Downstream antisense transcription initiates between nucleosomes regularly positioned downstream of gene transcription start sites. Those nucleosomes between gene and downstream antisense transcription start sites carry histone modifications associated with active promoters, such as H3K4me3 and H3K27ac. Strikingly, this same region is bound by chromatin remodeling complexes such as HDAC and SWI/SNF. The coincidence of transcription initiation with nucleosomes displaying promoter-associated histone marks underlies an apparent connection between antisense transcription and the chromatin environment at gene promoters. The association of chromatin remodelers at sites of downstream antisense transcription initiation suggests that antisense transcription contributes to the deposition and maintenance of these chromatin features at gene promoters.
Project description:Bread wheat is the major staple food of the world with a complex hexaploidy genome. The precise spatiotemporal gene expression is orchestrated by enhancers, which lack general sequence features and thus are difficult to be located, especially in large genomes. Epigenomic architecture, including chromatin openness and active chromatin marks, has been widely used to characterize enhancers. However, an active chromatin environment does not necessarily mean an active enhancer. Recently, enhancer RNAs (eRNAs), the hallmark for active enhancers, have been detected by nascent RNA sequencing in both Drosophila and mammalian. In order to answer whether plant enhancers could be transcribed, we investigated the transcriptome of bread wheat via two nascent RNA sequencing methods, GRO-seq and pNET-seq combining with epigenome profiling. Our study demonstrates the presence and wide distribution of transcription at intergenic enhancers, which accurately reflects high enhancer activity, shedding light on the complex gene expression regulation across subgenomes in bread wheat.