Transcription shapes DNA replication initiation to preserve genome integrity
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus Homo sapiens
PROVIDER: GSE174680 | GEO | 2021/05/20
REPOSITORIES: GEO
Similar Datasets
Project description:Sumoylation is emerging as a post-translation modification important for chromosome duplication and stability. The origin recognition complex (ORC), which directs DNA replication initiation by loading the MCM replicative helicases onto origins, is sumoylated in both yeast and human cells. However, the biological consequences of ORC sumoylation are largely unclear. Here we report the effects of hyper- and hypo-sumoylation of yeast ORC using multiple approaches. We show that ORC hyper-sumoylation preferentially reduces the activity of a subset of early origins, while Orc2 hypo-sumoylation has an opposing effect. Mechanistically, ORC hyper-sumoylation leads to reduced MCM loading in vitro and diminished MCM chromatin association in vivo. The importance of an appropriate level of ORC sumoylation is suggested by the data that either hyper- or hypo-sumoylation of ORC results in genome instability and a dependence on other genome maintenance factors for cell fitness. Thus, yeast ORC sumoylation status needs to be fine-tuned to achieve optimal origin activity control and genome stability.
2023-03-11 | PXD032977 | Pride
Project description:The Origin Recognition Complex (ORC) is essential for the initiation of eukaryotic chromosome replication as it loads the replicative helicase, the minichromosome maintenance (MCM) complex, at replication origins. Origins display a stereotypic chromatin structure with nucleosome depletion at ORC binding sites and flanking arrays of regularly spaced nucleosomes. Although discovered long ago, it is unknown how this chromatin struture is established and if it matters for replication. By genome-scale biochemical reconstitution we screened ~300 origins and 17 purified budding yeast chromatin factors and found that ORC established nucleosome depletion over origins and flanking nucleosome arrays by orchestrating the chromatin remodelers INO80, ISW1a, ISW2 and Chd1. The functional importance of ORC’s chromatin organizing activity was directly demonstrated by ORC mutations that maintained classical MCM loader activity but lost array generation activity. These mutations impaired replication through chromatin in vitro and were lethal in vivo. Our results establish that ORC, besides its canonical role as MCM loader, has a second essential function as master regulator of the origin chromatin structure that is a crucial prerequisite for efficient chromosome replication.
2023-03-30 | GSE209681 | GEO
Project description:The origin recognition complex (ORC) marks chromosomal sites as replication origins and is essential for replication initiation. In yeast, ORC also binds to DNA elements called silencers, where its primary function is to recruit silent information regulator (SIR) proteins to establish transcriptional silencing. Indeed, silencers function poorly as chromosomal origins. Several genetic, molecular, and biochemical studies of HMR-E have led to a model proposing that when ORC becomes limiting in the cell, such as in the orc2-1 mutant, only sites that bind ORC tightly, such as HMR-E, remain fully occupied by ORC, while lower affinity sites, including most origins, lose ORC occupancy. Since HMR-E possessed a unique non-replication function, we reasoned that other tight sites might reveal novel functions for ORC on chromosomes. Therefore, we comprehensively determined ORC “affinity” genome-wide by performing an ORC ChIP-on-chip in ORC2 and orc2-1 strains. Here we describe a novel group of orc2-1-resistant ORC-interacting chromosomal sites (ORF-ORC sites) that did not function as replication origins or silencers. Instead, ORF-ORC sites were comprised of protein-coding regions of highly transcribed metabolic genes. In contrast to the ORC-silencer paradigm, transcriptional activation promoted ORC association with these genes. Remarkably, ORF-ORC genes were enriched in proximity to origins of replication, and, in several instances, were transcriptionally regulated by these origins. Taken together, these results suggest a surprising connection between ORC, replication origins and cellular metabolism.
2009-11-07 | GSE18895 | GEO
Project description:The minichromosome maintenance complex (MCM) DNA helicase is an important replicative factor during DNA replication. The proper chromatin loading of MCM is a key step to ensure replication initiation during G1/S phase. Because replication initiation is regulated by multiple biological cues, additional changes to MCM may provide deeper understanding towards this event. Here, we uncover that the histidine methyltransferase SETD3 promotes DNA replication in an enzymatic activity dependent manner. Nascent-strand sequencing (NS-seq) shows that SETD3 regulates replication initiation, as depletion of SETD3 attenuates early replication origins firing. Mechanistically, biochemical experiments reveal that SETD3 binds MCM mainly during G1/S phase, which is required for CDT1-mediated chromatin loading of MCM. The MCM loading relies on the histidine-459 methylation (H459me) on MCM7 that is catalyzed by SETD3. Impairment of H459 methylation attenuates DNA synthesis and chromatin loading of MCM. Furthermore, we show that CDK2 phosphorylates SETD3 at Serine-21 during the G1/S phase, which is required for DNA replication and cell cycle progression. These findings demonstrate a novel mechanism by which SETD3 methylates MCM to regulate replication initiation.
2024-03-12 | GSE243937 | GEO
Project description:There are approximately 500 known origins of replication in the yeast genome, and the process by which DNA replication initiates at these locations is well understood. In particular, these sites are made competent to initiate replication by loading of the Mcm replicative helicase prior to the start of S phase; thus, "a site to which MCM is bound in G1" might be considered to provide an operational definition of a replication origin. By fusing a subunit of Mcm to micrococcal nuclease, a technique referred to as "Chromatin Endogenous Cleavage", we previously showed that known origins are typically bound by a single Mcm double hexamer, loaded adjacent to the ARS consensus sequence (ACS). Here we extend this analysis from known origins to the entire genome, identifying candidate Mcm binding sites whose signal intensity varies over at least 3 orders of magnitude. Published data quantifying the production of ssDNA during S phase showed clear evidence of replication initiation among the most abundant 1600 of these sites, with replication activity decreasing in concert with Mcm abundance and disappearing at the limit of detection of ssDNA. Three other hallmarks of replication origins were apparent among the most abundant 5,500 sites. Specifically, these sites (1) appeared in intergenic nucleosome-free regions that were flanked on one or both sides by well-positioned nucleosomes; (2) were flanked by ACSs; and (3) exhibited a pattern of GC skew characteristic of replication initiation. Furthermore, the high resolution of this technique allowed us to demonstrate a strong bias for detecting Mcm double-hexamers downstream rather than upstream of the ACS, which is consistent with the directionality of Mcm loading by Orc that has been observed in vitro. We conclude that DNA replication origins are at least 3-fold more abundant than previously assumed, and we suggest that replication may occasionally initiate in essentially every intergenic region. These results shed light on recent reports that as many as 15% of replication events initiate outside of known origins, and this broader distribution of replication origins suggest that S phase in yeast may be less distinct from that in humans than is widely assumed.
2023-09-05 | GSE242131 | GEO
Project description:During DNA replication initiation, the Origin Recognition Complex (ORC) and Cdc6 co-associate on DNA to load replicative helicases onto origins of replication. We apply DSSO crosslinking mass spectrometry of reconstituted ORC-DNA-Cdc6 to identify interactions between different subunits and domains in the complex.
2022-02-28 | PXD031033 | Pride
Project description:The origin recognition complex (ORC) nucleates DNA replication initiation in eukaryotic cells. This six-protein complex binds replication origin DNA, recruits other initiation factors and facilitates loading of the DNA helicase. Studying the function of individual ORC subunits during pre-RC formation has been hampered by the requirement of most subunits for DNA binding. In this study, we investigate the function of the S. cerevisiae Orc6 subunit, the only subunit not required for DNA binding. In vivo, depletion of Orc6 inhibits pre-replicative complex (pre-RC) assembly and maintenance. In vitro, ORC lacking Orc6 fails to interact with Cdt1 and to load the Mcm2-7 helicase onto origin DNA. We demonstrate that two regions of Orc6 bind Cdt1 directly and that the extreme C-terminus of Orc6 (Orc6-CTD) interacts tightly with the remaining five ORC subunits. Replacing Orc6 with a fusion protein linking Cdt1 to the Orc6-CTD results in an ORC complex that loads Mcm2-7 onto DNA. Interestingly, this complex can only perform a single round of Mcm2-7 loading, suggesting that a dynamic association of Cdt1 with ORC is required for multiple rounds of pre-RC assembly. Keywords: ChIP-chip
2007-11-14 | GSE9318 | GEO
Project description:Mini-chromosome maintenance (MCM) proteins are loaded to chromatin during G1-phase and define potential locations of DNA replication initiation. MCM protein deficiency results in genome instability and high rates of cancer in mouse models. Here we develop a method of nascent strand capture and release and show that MCM2 deficiency reduces DNA replication initiation in gene rich regions of the genome. DNA structural properties are shown to correlate with sequence motifs associated with replication origins and with locations that are preferentially affected by MCM2 deficiency. Reduced nascent strand density correlates with sites of recurrent focal CNVs in tumors arising in MCM2-deficient mice, consistent with a direct relationship between sites of reduced DNA replication initiation and genetic damage. Between 10 and 90% of human tumors, depending on type, carry heterozygous loss or mutation of one or more Mcm2-7 genes which is expected to compromise DNA replication origin licensing and result in elevated rates of genome damage at a subset of gene rich locations. Mcm2 deficient vs. wild type
2015-01-14 | E-GEOD-64933 | biostudies-arrayexpress
Project description:The hexameric DNA helicase MCM (Mcm2-7) is a central regulatory target in eukaryotic replication. Chromatin-bound MCM is kept inactive during G1 phase and subsequently activated in S phase to initiate replication. During this transition, the only known chemical change on the Mcm2-7 proteins is the gain of multi-site phosphorylation that promotes recruitment of co-factors. As replication initiation is tied intimately to multiple biological cues, additional changes on these proteins can provide a second regulatory point. Here we describe a new MCM modification cycle mediated by SUMO that enables a negative regulation of replication initiation. We show that all MCM subunits undergo sumoylation upon loading at origins in G1 phase prior to MCM phosphorylation. Then bulk MCM sumoylation is lost as MCM phosphorylation rises. The pattern of MCM sumoylation suggests a negative role in replication. Indeed, increasing MCM sumoylation delays genome-wide replication initiation. Mechanistically, this is partly due to enhancing the recruitment of a conserved phosphatase that delays MCM phosphorylation and activation. By revealing a new MCM modification cycle and its role in replication, our findings suggest a new model, in which MCM sumoylation counterbalances kinase-based regulation to ensure accurate control of replication initiation.
2016-02-01 | GSE70407 | GEO
Project description:Eukaryotic genomes are replicated from many origin sites that are licensed by the loading of inactive double hexamers of the replicative DNA helicase, Mcm2-7. How eukaryotic origin positions are specified remains elusive. Here we show that, contrary to the bacterial paradigm, eukaryotic origins are not irrevocably defined by selection of the loading site for the replicative helicase, but can shift in position after helicase loading. Using purified proteins, we show that DNA translocases, including RNA polymerase, can push budding yeast Mcm2-7 double hexamers along DNA. Displaced Mcm2-7 double hexamers support DNA replication initiation distal to the loading site in vitro. In yeast cells that are defective for transcription termination, collisions with RNA polymerase induce a shift in origin positions that correlates with the direction of transcription. These results reveal a eukaryotic origin specification mechanism that departs from the classical replicon model, helping eukaryotic cells to negotiate transcription-replication conflict. 4 samples: one replicate for WT at 37C, two replicates for rat1-1 at 37C, and one replicate for rat1-1 at 24C. All are single-end sequenced via Ion Torrent PGM methodology. rat1 = Nuclear 5' to 3' single-stranded RNA exonuclease; involved in RNA metabolism (http://www.yeastgenome.org/locus/S000005574/overview). 4 ChIP seq samples and their duplicates are submitted. rat1-1 ORC ChIP at 24C and 37C; rat1-1 MCM ChIP at 24C and 37C.
2016-01-07 | E-GEOD-69065 | biostudies-arrayexpress