Homo sapiens
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ABSTRACT:
PROVIDER: PRJNA369608 | ENA |
REPOSITORIES: ENA
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Project description:Chromatin structure affects DNA replication patterns, but the role of specific chromatin modifiers in regulating the replication process is yet unclear. We report that phosphorylation of the human SIRT1 deacetylase on Threonine 530 (T530-pSIRT1) modulates DNA synthesis. T530-pSIRT1 associates with replication origins and inhibits replication from a group of ÒdormantÓ potential replication origins, which initiate replication only when cells are subject to replication stress. Although both active and dormant origins bind T530-pSIRT1, active origins are distinguished from dormant origins by their unique association with an open chromatin mark, histone H3 methylated on lysine 4. SIRT1 phosphorylation also facilitates leading and lagging strand coordination. SIRT1 T530 phosphorylation is essential to prevent DNA breakage upon replication stress and cells harboring SIRT1 that cannot be phosphorylated exhibit a high prevalence of extrachromosomal elements, hallmarks of perturbed replication. These observations suggest that SIRT1 phosphorylation modulates the distribution of replication initiation events to insure genomic stability.
2017-06-02 | GSE94403 | GEO
Project description:In metazoans, the largest sirtuin, SIRT1, is a nuclear protein implicated in epigenetic modifications, circadian signaling, DNA recombination, replication and repair. Our previous studies have demonstrated that SIRT1 binds replication origins and inhibits replication initiation from a group of potential initiation sites (dormant origins). We studied the effects of aging and SIRT1 activity on replication origin usage and the incidence of transcription-replication collisions (creating R-loop structures) in adult human cells obtained at different time points during chronological aging and in cancer cells. In primary, untransformed cells, SIRT1 activity declined, and the prevalence of R-loops rose with chronological aging. Both the reduction of SIRT1 activity and the increased abundance of R-loops were also observed during the passage of primary cells in culture. All cells, regardless of donor age or transformation status, reacted to short-term, acute chemical inhibition of SIRT1 with the activation of excessive replication initiation events coincident with an increased prevalence of R-loops. However, only cancer cells showed genome-wide activation of dormant origins during long-term proliferation with mutated or depleted SIRT1, whereas in primary cells, aging-associated SIRT1-mediated activation of dormant origins was restricted to rDNA loci. These observations suggest that chronological aging and the associated decline in SIRT1 activity relaxes the regulatory networks that protect cells against excess replication and that the mechanisms protecting from replication-transcription collisions at the rDNA loci manifest as a differentially enhanced sensitivity to SIRT1 decline and chronological aging.
2023-11-27 | GSE247469 | GEO
Project description:Mammalian DNA replication starts at distinct chromosomal sites in a tissue-specific pattern coordinated with transcription, but previous studies have not yet identified a chromatin modification that correlates with the initiation of DNA replication. This submission is associated with a paper in which we report that replication initiation events are associated with a high frequency of methylation of histone H3 on lysine K79 (H3K79Me2 and H3K79Me3). H3K79Me2-containing chromatin exhibited the highest enrichment of replication initiation events observed in a single chromatin modification. Importantly, H3K79 methylation was enriched in chromatin containing a replicator (a DNA sequence capable of initiating DNA replication), but not in chromatin containing a mutant replicator that could not initiate replication. The association of H3K79Me2 with replication initiation sites was independent and not synergistic with other chromatin modifications. H3K79 methylation exhibited a wider distribution and greater abundance during S-phase, but regions of chromatin that were only modified during S-phase were not enriched in replication initiation events. In addition, the paper shows that depletion of DOT1L, the sole enzyme responsible for H3K79 methylation, triggered limited genomic over-replication. These data are consistent with the hypothesis that methylation of H3K79 associates with replication origins and marks replicated chromatin during S-phase to prevent re-replication and preserve genomic stability. Evaluation of HeK79 methylation in chromatin samples from cell cycle fractionated K562 leukemia cells. Unsyncrhonized untreated cultures of K562 cells were fractionated by size using centrifugal elutriation. Chromatin was isolated and subject to ChIP-Seq with antibodies directed against dimethylated and trimethylated lysine on histone H3.
2013-06-06 | E-GEOD-35294 | biostudies-arrayexpress
Project description:During routine genome duplication, many potential replication origins remain inactive, or dormant. Such origin dormancy is achieved, in part, by an interaction with the metabolic sensor SIRT1 deacetylase. We report here that dormant origins are a group of consistent, pre-determined genomic sequences that can be distinguished from baseline (i.e. ordinarily active) origins by their preferential association with MCM2, a component of the replicative helicase, phosphorylated on serine 108 (pS108-MCM2). pS108-MCM2 is a substrate of the ATR kinase, which is recruited to chromatin via an interaction with hyperacetylated TOPBP1 in cells undergoing replication stress or in cells devoid of SIRT1 deacetylase activity. In turn, S108-MCM2 phosphorylation enhances a second, DDK-dependent, S139-MCM2 phosphorylation, which triggers initiation of DNA replication at dormant origins. These observations suggest that replication origin dormancy and activation are regulated by distinct post-translational modifications on the MCM helicase that reflect a balance between SIRT1 activity and ATR signaling.
| MSV000088134 | MassIVE
Project description:Safeguards against excess DNA replication are often dysregulated in cancer, and driving cancer cells towards over-replication is a promising therapeutic strategy. We determined DNA synthesis patterns in cancer cells undergoing partial genome re-replication due to perturbed regulatory interactions ("re-replicating cells"). These cells exhibited slow replication, increased frequency of replication initiation events and a skewed initiation pattern that preferentially reactivated early-replicating origins. Unlike in cells exposed to replication stress, which activated a novel group of hitherto unutilized (”dormant”) replication origins, the preferred re-replicating origins arose from the same pool of potential origins as those activated during normal growth. Mechanistically, the skewed initiation pattern reflected a disproportionate distribution of pre-replication complexes on distinct regions of licensed chromatin prior to replication. This distinct pattern suggests that circumventing the strong inhibitory interactions that normally prevent excess DNA synthesis can occur via at least two pathways, each activating a distinct set of replication origins.
2021-06-01 | GSE172417 | GEO
Project description:Mammalian DNA replication starts at distinct chromosomal sites in a tissue-specific pattern coordinated with transcription, but previous studies have not yet identified a chromatin modification that correlates with the initiation of DNA replication. This submission is associated with a paper in which we report that replication initiation events are associated with a high frequency of methylation of histone H3 on lysine K79 (H3K79Me2 and H3K79Me3). H3K79Me2-containing chromatin exhibited the highest enrichment of replication initiation events observed in a single chromatin modification. Importantly, H3K79 methylation was enriched in chromatin containing a replicator (a DNA sequence capable of initiating DNA replication), but not in chromatin containing a mutant replicator that could not initiate replication. The association of H3K79Me2 with replication initiation sites was independent and not synergistic with other chromatin modifications. H3K79 methylation exhibited a wider distribution and greater abundance during S-phase, but regions of chromatin that were only modified during S-phase were not enriched in replication initiation events. In addition, the paper shows that depletion of DOT1L, the sole enzyme responsible for H3K79 methylation, triggered limited genomic over-replication. These data are consistent with the hypothesis that methylation of H3K79 associates with replication origins and marks replicated chromatin during S-phase to prevent re-replication and preserve genomic stability.
2013-06-06 | GSE35294 | GEO
Project description:During routine genome duplication, many potential replication origins remain inactive, or 'dormant'. Such origin dormancy is achieved, in part, by an interaction with the metabolic sensor SIRT1 deacetylase. We report here that dormant origins are a group of consistent, pre-determined genomic sequences that can be distinguished from baseline (i.e. ordinarily active) origins by their preferential association with MCM2, a component of the replicative helicase, phosphorylated on serine 108 (pS108-MCM2). pS108-MCM2 is a substrate of the ATR kinase, which is recruited to chromatin via an interaction with hyperacetylated TOPBP1 in cells undergoing replication stress or in cells devoid of SIRT1 deacetylase activity. In turn, S108-MCM2 phosphorylation enhances a second, DDK-dependent, S139-MCM2 phosphorylation, which triggers initiation of DNA replication at dormant origins. These observations suggest that replication origin dormancy and activation are regulated by distinct post-translational modifications on the MCM helicase that reflect a balance between SIRT1 activity and ATR signaling.
2022-05-09 | GSE184353 | GEO
Project description:Background: Eukaryotic cells must inhibit re-initiation of DNA replication at each of the thousands of origins in their genome because re-initiation events can generate genomic alterations with extraordinary frequency. To minimize the probability of re-initiation from so many origins, cells use a battery of regulatory mechanisms that reduce the activity of replication initiation proteins. Given the global nature of these mechanisms, it has been presumed that all origins are inhibited identically. However, transiently disabling these mechanisms causes replication origins to re-initiate with diverse efficiencies, which do not correlate with known differences in the efficiency or timing of origin initiation during normal DNA replication. These observations suggest an additional local layer of replication control that can differentially influence how re-initiation is regulated at distinct origins. Principal Findings: We have identified novel genetic elements that are necessary for preferential re-initiation of two origins and sufficient to confer preferential re-initiation on heterologous origins when the control of re-initiation is partially deregulated. The elements do not enhance the S phase timing or efficiency of adjacent origins and thus are specifically acting as re-initiation promoters (RIPs). We have mapped the two RIPs to ~60bp AT rich sequences that act in a distance- and sequence-dependent manner. During the induction of re-replication, Mcm2-7 re-associates both with origins that preferentially re-initiate and origins that do not, suggesting that the RIP elements can overcome a block to re-initiation imposed after Mcm2-7 associates with origins. Conclusions/Significance: We have uncovered a local level of control in the block to re-initiation. This local control creates a complex genomic landscape of re-replication potential that is revealed when global mechanisms preventing re-replication are peeled away. Hence, if re-replication does contribute to genomic alterations, as has been speculated for cancer cells, some regions of the genome may be more susceptible to these alterations than others. 142 array CGH experiments are presented. Each experiment is done in experimental replicate. Cells grown as described in Richardson CD and Li JJ PLoS Genetics 2014. Ch1 samples taken from replicating (S phase) or re-replicating (M phase + 3/6 hour induced). Ch2 samples taken from M phase arrested DNA.
2014-03-15 | E-GEOD-55420 | biostudies-arrayexpress
Project description:Eukaryotic cells must inhibit re-initiation of DNA replication at each of the thousands of origins in their genome because re-initiation can generate genomic alterations with extraordinary frequency. To minimize the probability of re-initiation from so many origins, cells use a battery of regulatory mechanisms that reduce the activity of replication initiation proteins. Given the global nature of these mechanisms, it has been presumed that all origins are inhibited identically. However, origins re-initiate with diverse efficiencies when these mechanisms are disabled, and this diversity cannot be explained by differences in the efficiency or timing of origin initiation during normal S phase replication. This observation raises the possibility of an additional layer of replication control that can differentially regulate re-initiation at distinct origins. We have identified novel genetic elements that are necessary for preferential re-initiation of two origins and sufficient to confer preferential re-initiation on heterologous origins when the control of re-initiation is partially deregulated. The elements do not enhance the S phase timing or efficiency of adjacent origins and thus are specifically acting as re-initiation promoters (RIPs). We have mapped the two RIPs to ~60 bp AT rich sequences that act in a distance- and sequence-dependent manner. During the induction of re-replication, Mcm2-7 reassociates both with origins that preferentially re-initiate and origins that do not, suggesting that the RIP elements can overcome a block to re-initiation imposed after Mcm2-7 associates with origins. Our findings identify a local level of control in the block to re-initiation. This local control creates a complex genomic landscape of re-replication potential that is revealed when global mechanisms preventing re-replication are compromised. Hence, if re-replication does contribute to genomic alterations, as has been speculated for cancer cells, some regions of the genome may be more susceptible to these alterations than others.
2014-03-15 | GSE55420 | GEO
Project description:SIRT1 chromatin interactome analysis was performed to identify SIRT1 molecular targets involved in replication initiation from cells containing either WT or H363Y SIRT1. Co-IP-MS of pT530 SIRT1 from chromatin extracts was performed. Files are: 1422 WT SIRT1 untreated U2OS; 1423 WT SIRT1 H2O2 treated, U2OS; 1424 H363Y SIRT1 untreated U2OS; 1425 H363Y SIRT1 H2O2 U2OS; 1426 KO SIRT1 untreated U2OS; 1427 KO SIRT1 H2O2 U2OS; 1428 WT SIRT1 untreated HEK; 1429 WT SIRT1 H2O2 HEK; 1430 WT SIRT1 untreated HCT116; 1431 WT SIRT1 H2O2 HCT116; 1432 WT SIRT1 untreated K562; 1433 WT SIRT1 H2O2 K562. Each sample has 9 fractions.
| MSV000088103 | MassIVE