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:Faithful genome duplication requires coordination between transcription and replication. Disruption of this coordination causes transcription-replication conflicts (TRCs), leading to replication stress and genome instability. How chromatin regulators modulate these processes remains unclear. Here, we show that the Rpd3L histone deacetylase complex dynamically modulates chromatin state to control replication fork progression and buffer TRCs in Saccharomyces cerevisiae. Rpd3L is targeted through both histone H3 lysine 4 methylation-dependent recruitment and methylation-independent mechanisms engaged under replication stress. Loss of H3K4 methylation or Rpd3L function promotes histone acetylation, accelerates fork progression through transcribed regions, and increases transcription-associated genome instability. Balanced acetylation at multiple histone lysines is required to stabilize replication forks under stress. While histone deacetylase complexes have been implicated in repairing damaged forks, our findings reveal that Rpd3L acts preemptively to modulate chromatin state and replication dynamics during TRCs, defining a chromatin-based mechanism that safeguards genome stability.
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: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.