Project description:Whole genome profiling of 4 histone modifications (H3K27me1, H3K27me3,H3K36me1 and H3K36me3) using ChIP-on-chip. It has recently been shown that nucleosome distribution, histone modifications and RNA polymerase II (Pol II) occupancy show preferential association with exons ("exon-intron marking"), linking chromatin structure and function to co- transcriptional splicing in a variety of eukaryotes. Previous ChIP-sequencing studies suggested that these marking patterns reflect the nucleosomal landscape. By analyzing ChIP-chip datasets across the human genome in three cell types, we have found that this marking system is far more complex than previously observed. We show here that a range of histone modifications and Pol II are preferentially associated with exons. However, there is noticeable cell-type specificity in the degree of exon marking by histone modifications and, surprisingly, this is also reflected in some histone modifications patterns showing biases towards introns. Exon-intron marking is laid down in the absence of transcription on silent genes, with some marking biases changing or becoming reversed for genes expressed at different levels. Furthermore, the relationship of this marking system with splicing is not simple, with only some histone modifications reflecting exon usage/inclusion, while others mirror patterns of exon exclusion. By examining nucleosomal distributions in all three cell types, we demonstrate that these histone modification patterns cannot solely be accounted for by differences in nucleosome levels between exons and introns. In addition, because of inherent differences between ChIP-chip array and ChIP-sequencing approaches, these platforms report different nucleosome distribution patterns across the human genome. Our findings confound existing views and point to active cellular mechanisms which dynamically regulate histone modification levels and account for exon-intron marking. We believe that these histone modification patterns provide links between chromatin accessibility, Pol II movement and co-transcriptional splicing.
Project description:Transcription profiling of two cancer cell lines: K562 and U937. It has recently been shown that nucleosome distribution, histone modifications and RNA polymerase II (Pol II) occupancy show preferential association with exons ("exon-intron marking"), linking chromatin structure and function to co- transcriptional splicing in a variety of eukaryotes. Previous ChIP-sequencing studies suggested that these marking patterns reflect the nucleosomal landscape. By analyzing ChIP-chip datasets across the human genome in three cell types, we have found that this marking system is far more complex than previously observed. We show here that a range of histone modifications and Pol II are preferentially associated with exons. However, there is noticeable cell-type specificity in the degree of exon marking by histone modifications and, surprisingly, this is also reflected in some histone modifications patterns showing biases towards introns. Exon-intron marking is laid down in the absence of transcription on silent genes, with some marking biases changing or becoming reversed for genes expressed at different levels. Furthermore, the relationship of this marking system with splicing is not simple, with only some histone modifications reflecting exon usage/inclusion, while others mirror patterns of exon exclusion. By examining nucleosomal distributions in all three cell types, we demonstrate that these histone modification patterns cannot solely be accounted for by differences in nucleosome levels between exons and introns. In addition, because of inherent differences between ChIP-chip array and ChIP-sequencing approaches, these platforms report different nucleosome distribution patterns across the human genome. Our findings confound existing views and point to active cellular mechanisms which dynamically regulate histone modification levels and account for exon-intron marking. We believe that these histone modification patterns provide links between chromatin accessibility, Pol II movement and co-transcriptional splicing.
Project description:Chromatin immunoprecipitation microarray (ChIP-chip) study using 3 human cell lines (K562, U937, CD14+); of 19 histone modifications across 1% of the human genome used in the pilot phase of the ENCODE project.<br>paper abstract: It has recently been shown that nucleosome distribution, histone modifications and RNA polymerase II (Pol II) occupancy show preferential association with exons ("exon-intron marking"), linking chromatin structure and function to co- transcriptional splicing in a variety of eukaryotes. Previous ChIP-sequencing studies suggested that these marking patterns reflect the nucleosomal landscape. By analyzing ChIP-chip datasets across the human genome in three cell types, we have found that this marking system is far more complex than previously observed. We show here that a range of histone modifications and Pol II are preferentially associated with exons. However, there is noticeable cell-type specificity in the degree of exon marking by histone modifications and, surprisingly, this is also reflected in some histone modifications patterns showing biases towards introns. Exon-intron marking is laid down in the absence of transcription on silent genes, with some marking biases changing or becoming reversed for genes expressed at different levels. Furthermore, the relationship of this marking system with splicing is not simple, with only some histone modifications reflecting exon usage/inclusion, while others mirror patterns of exon exclusion. By examining nucleosomal distributions in all three cell types, we demonstrate that these histone modification patterns cannot solely be accounted for by differences in nucleosome levels between exons and introns. In addition, because of inherent differences between ChIP-chip array and ChIP-sequencing approaches, these platforms report different nucleosome distribution patterns across the human genome. Our findings confound existing views and point to active cellular mechanisms which dynamically regulate histone modification levels and account for exon-intron marking. We believe that these histone modification patterns provide links between chromatin accessibility, Pol II movement and co-transcriptional splicing.
Project description:Transcription factors represent one of the largest groups of proteins regulated by SUMO, and their modification has generally been correlated with transcriptional repression. However, as most of the studies focus on specific sumoylated transcriptional regulators, the distribution and global role of SUMO on chromatin in relation to transcription regulation remain largely unknown. To investigate this role, we determined the occupancy of SUMO machinery proteins on chromatin by ChIP coupled to sequencing in human primary cells. Examination of 3 histone modifications, Polymerase II, SUMO1, SUMO2, Ubc9 and PIASy in proliferative and Ras-induced senescent fibroblasts.
Project description:We report the application of single molecule-based sequencing technology for high-throughput mapping of CFP1, RNA polymerase II and H3K4me3 in mouse brain. By obtaining sequence from chromatin immunoprecipitated DNA, we generated genome-wide binding / chromatin-state maps for mouse brain. We find a good correlation between CFP1 binding and H3K4me3 consistent with it presence in the SetD1 histone methylatransferase complex. Mapped RNA polymerase II colocalised with the majority of CFP1 / H3K4me3 positive CpG islands but not all. This study provides a comprehensive characterisation of the genome wide distribution of a previously uncharacaterised DNA binding factor and suggests a link between DNA base composition and chromatin state. Examination of H3K4me3, RNA PolymeraseII and CFP1 in mouse brain.
Project description:We report the application of single molecule-based sequencing technology for high-throughput mapping of CFP1, RNA polymerase II and H3K4me3 in mouse brain. By obtaining sequence from chromatin immunoprecipitated DNA, we generated genome-wide binding / chromatin-state maps for mouse brain. We find a good correlation between CFP1 binding and H3K4me3 consistent with it presence in the SetD1 histone methylatransferase complex. Mapped RNA polymerase II colocalised with the majority of CFP1 / H3K4me3 positive CpG islands but not all. This study provides a comprehensive characterisation of the genome wide distribution of a previously uncharacaterised DNA binding factor and suggests a link between DNA base composition and chromatin state.
Project description:Several lines of recent evidence support a role for chromatin in splicing regulation. Here we show that splicing can also contribute to histone modification, which implies a bidirectional communication between epigenetics and RNA processing. Genome-wide analysis of histone methylation in human cell lines and mouse primary T cells reveals that intron-containing genes are preferentially marked with H3K36me3 relative to intronless genes. In intron-containing genes, H3K36me3 marking is proportional to transcriptional activity, whereas in intronless genes H3K36me3 is always detected at much lower levels. Furthermore, splicing inhibition impairs recruitment of H3K36 methyltransferase HYPB/Setd2 and reduces H3K36me3, whereas splicing activation has the opposite effect. Moreover, the increase of H3K36me3 correlates with the length of the first intron, consistent with the view that splicing enhances H3 methylation. We propose that splicing is mechanistically coupled to recruitment of HYPB/Setd2 to elongating RNA Polymerase II. This experiment proposes to profile genome-wide binding profiles by ChIP-seq (Illumina, 36 bp tags) of RNA polymerase II (one biological replicate), the histone modification H3K36me3 (2 replicates) and a reference control input sample (genomic DNA after reverse cross-link, one replicate) in a human H1299 lung carcinoma cell line *** Raw data not provided for Samples GSM766322-GSM766324.
Project description:While Argonaute (AGO) proteins play a major role in transcriptional gene silencing (TGS) in many organisms, their role in the nucleus of somatic mammalian cells remains elusive. Here, we have purified AGO1 and AGO2 chromatin-embedded complexes, and found these proteins associated with previously described partners, but also with chromatin modifiers and, rather unexpectedly, with different splicing factors. Using the CD44 gene as a model for alternative splicing, we show that both AGO1 and AGO2 are required for Protein Kinase C (PKC)-dependent variant exon inclusion. AGO proteins facilitate the spliceosome recruitment and modulate the elongation rate of RNA polymerase II (RNAPII). The recruitment of AGO proteins to CD44 transcribed region is dependent on both the endonuclease Dicer and the chromodomain-containing protein HP1g, and results in locally increased levels of histone H3 lysine 9 (H3K9) methylation on variant exons. Genome wide analysis of splicing in either AGO2 or Dicer null cells showed that the two proteins have similar effects on many splicing events. Finally, sRNAs associated with nuclear AGO2 are mostly in sense orientation relative to protein-coding genes, supporting a role for intragenic antisense non-coding RNAs in the recruitment AGO and splicing factors. Together, our data demonstrate for the first time that the endogenous RNAi pathway is involved in alternative splicing decisions, unravelling a new model in which AGO proteins couple RNAPII elongation and chromatin modification. Study of AGO2 or Dicer knock-out on gene expression and splicing regulation in MEF cells Transcriptome analysis of AGO2 and Dicer null MEF cells on GeneChipM-BM-. Mouse Exon 1.0 ST Arrays (Affymetrix). Dicer null MEF cells and wild-type MEF cells were from M. Otsuka. AGO2 null MEF cells were from A. Tarakhovsky. Experiment has been done in experimental triplicates. 9 Total samples were analyzed.