Project description:The eukaryotic genome is organized into chromatins, the physiological template for DNA-dependent processes including replication, recombination, repair, and transcription. Chromatin-mediated transcription regulation involves DNA methylation, chromatin remodeling, and histone modifications. However, chromatin also contains non-histone chromatin-associated proteins, of which the high-mobility group (HMG) proteins are the most abundant. Although it is known that HMG proteins induce structural changes of chromatin, the processes underlying transcription regulation by HMG proteins are poorly understood. Here we decipher the molecular mechanism of transcription regulation mediated by the HMG AT-hook 2 protein (HMGA2). We combined proteomic, ChIP-seq, and transcriptome data to show that HMGA2-induced transcription requires phosphorylation of the histone variant H2AX at S139 (H2AXS139ph; γ-H2AX) mediated by the protein kinase ataxia telangiectasia mutated (ATM). Furthermore, we demonstrate the biological relevance of this mechanism within the context of TGFβ1 signaling. The interplay between HMGA2, ATM, and H2AX is a novel mechanism of transcription initiation. Our results link H2AXS139ph to transcription, assigning a new function for this DNA damage marker. Controlled chromatin opening during transcription may involve intermediates with DNA breaks that may require mechanisms that ensure the integrity of the genome.
Project description:The 3-dimensional (3D) conformation of chromatin inside the nucleus is integral to a variety of nuclear processes including transcriptional regulation, DNA replication, and DNA damage repair. Aberrations in 3D chromatin conformation have been implicated in developmental abnormalities and cancer. Despite the importance of 3D chromatin conformation to cellular function and human health, little is known about how 3D chromatin conformation varies in the human population, or whether DNA sequence variation between individuals influences 3D chromatin conformation. To address these questions, we performed Hi-C on Lymphoblastoid Cell Lines (LCLs) from a panel of 20 individuals. We identify thousands of regions across the genome where 3D chromatin conformation varies between individuals and find that these conformational variations are often accompanied by variations in gene expression, histone modifications, and transcription factor (TF) binding. Moreover, we find that DNA sequence variation influences several features of 3D chromatin conformation including loop strength, contact insulation, contact directionality and density of local cis contacts. We map hundreds of Quantitative Trait Loci (QTLs) associated with 3D chromatin features and find evidence that some of these same variants are associated at modest levels with other molecular phenotypes as well as complex disease risk. Our results demonstrate that common DNA sequence variants can influence 3D chromatin conformation, pointing to a more pervasive role for 3D chromatin conformation in human phenotypic variation than previously recognized.
Project description:Linker histones are highly abundant chromatin-associated proteins with well-established structural roles in chromatin and as general transcriptional repressors. In addition, it has been long proposed that histone H1 exerts context-specific effects on gene expression. Here, we have identified a new function of histone H1 in chromatin structure and transcription using a range of genomic approaches. We show that histone H1-depleted cells accumulate nascent non-coding RNAs on chromatin, suggesting that histone H1 prevents non-coding RNA transcription and regulates non-coding transcript turnover on chromatin. Accumulated non-coding transcripts have reduced levels of m6A modification causing replication-transcription conflicts. Accordingly, altering the m6A RNA methylation pathway rescues the replicative phenotype of H1 loss. This work unveils unexpected regulatory roles of histone H1 on non-coding RNA turnover and m6A deposition, highlighting the intimate relationship between chromatin conformation, RNA metabolism and DNA replication to maintain genome performance.
Project description:We describe how the cancer-causing Epstein-Barr virus (EBV), a prototypic herpesvirus, alters proteome at viral replication forks prominently identifies chromatin modifying and transcriptional repression proteins. Specifically, to transition from transcription, the viral DNA polymerase processivity factor EA-D is SUMOylated by the transcriptional corepressor KAP1-TRIM28. KAP1 function is triggered by phosphorylation via the PI3K-related kinase ATM and the helicase RECQ5 at the transcription machinery. SUMO-EA-D recruits the histone loader CAF1 and the methyltransferase SETDB1 to silence the parental genome, prioritizing replication. Thus, DNA repair, epigenetic, and transcription-replication interference pathways orchestrate the handover from transcription to replication, a fundamental feature of DNA viruses
Project description:ATP-dependent chromatin remodeling complexes have been shown to participate in DNA replication in addition to transcription and DNA repair. However, the mechanisms of their involvement in DNA replication remain unclear. Here, we reveal a specific function of the yeast INO80 chromatin remodeling complex in the DNA damage tolerance pathways. Whereas INO80 is necessary for the resumption of replication at forks stalled by methyl methane sulfonate (MMS), it is not required for replication fork collapse after treatment with hydroxyurea (HU). Mechanistically, INO80 regulates DNA damage tolerance during replication through modulation of PCNA (proliferating cell nuclear antigen) ubiquitination and Rad51-mediated processing of recombination intermediates at impeded replication forks. Our findings establish a mechanistic link between INO80 and DNA damage tolerance pathways, indicating that chromatin remodeling is important for accurate DNA replication. INO80 distribution in WT cells was measured.
Project description:The INO80 complex is a chromatin remodeler that regulates DNA replication, repair, and transcription. Although the INO80 complex plays a crucial role in various chromatin-associated processes, the mechanism of its recruitment to specific genomic loci is not well understood. Here we used a native ChIP-MS approach to quantitatively profile modifications present on nucleosomes co-purified with INO80 from MNAse-digested HeLa chromatin.
Project description:The INO80 complex is a chromatin remodeler that regulates DNA replication, repair, and transcription. Although the INO80 complex plays a crucial role in various chromatin-associated processes, the mechanism of its recruitment to specific genomic loci is not well understood. Here we used a native ChIP-MS approach to quantitatively profile modifications present on nucleosomes co-purified with INO80 from MNAse-digested HeLa chromatin.
Project description:In this study we characterized the importance of CDK12-kinase activity in cell cycle regulation, using CDK12 anolog-sentive cells. Inhibition of analog-sensitive CDK12 reveals its catalytic activity is necessary for optimal G1/S progression. Mechanistically, CDK12 regulates transcription of core DNA replication genes and affects timely assembly of pre-replication DNA complex on chromatin. We have performed 3’-end RNA-sequencing after CDK12 inhibition and identified that the expression of core DNA replication genes were affected. To investigate further, we carried out nuclear RNA-seq coupled with ChIP-seq, and demonstrated that CDK12 regulates RNAPII processivity of core DNA replication genes and optimal G1/S progression.