Project description:Quiescent hematopoietic stem cells (HSCs) are prone to mutagenesis, and accumulation of mutations can result in hematological malignancies. The mechanisms through which HSCs prevent such detrimental accumulation, however, are unclear. Here, we show that Aspp1 coordinates with p53 to maintain the genomic integrity of the HSC pool. Aspp1 is preferentially expressed in HSCs and restricts HSC pool size by attenuating self-renewal under steady state conditions. After genotoxic stress, Aspp1 promotes HSC cycling and induces p53-dependent apoptosis in cells with persistent DNA damage foci. Beyond these p53-dependent functions, Aspp1 attenuates HSC self-renewal and accumulation of DNA damage in p53-null HSCs. Consequently, concomitant loss of Aspp1 and p53 leads to the development of hematological malignancies, especially T-cell leukemia and lymphoma. Together, these data highlights coordination between Aspp1 and p53 in regulating HSC self-renewal and DNA damage tolerance, and suggest that HSCs possess specific mechanisms that prevent accumulation of mutations and malignant transformation. 8-week-old WT, Aspp1-/-, Mx1-Cre(+)p53flox/flox and Mx1-Cre(+)Aspp1-/-p53flox/flox mice were intraperitoneally administered with 400 μg pIpC five times every other day to obtain WT, Aspp1-/-, p53-/- and Aspp1-/-p53-/- bone marrow. 4 weeks after pIpC treatment, bone marrow lineage(-) Sca-1(+) cKit(+) cells were isolated. RNA was extracted and pooled from 3 independent mice per genotype. RNA samples were then amplified, labeled, and hybridized to independent arrays.
Project description:Barr2017 - Dynamics of p21 in hTert-RPE1
cells
This deteministic model reveals that a
bistable switch created by Cdt2, promotes irreversible S-phase
entry by keeping p21 levels low, prevents premature S-phase exit
upon DNA damage
This model is described in the article:
DNA damage during S-phase
mediates the proliferation-quiescence decision in the
subsequent G1 via p21 expression.
Barr AR, Cooper S, Heldt FS, Butera
F, Stoy H, Mansfeld J, Novák B, Bakal C.
Nat Commun 2017 Mar; 8: 14728
Abstract:
Following DNA damage caused by exogenous sources, such as
ionizing radiation, the tumour suppressor p53 mediates cell
cycle arrest via expression of the CDK inhibitor, p21. However,
the role of p21 in maintaining genomic stability in the absence
of exogenous DNA-damaging agents is unclear. Here, using live
single-cell measurements of p21 protein in proliferating
cultures, we show that naturally occurring DNA damage incurred
over S-phase causes p53-dependent accumulation of p21 during
mother G2- and daughter G1-phases. High p21 levels mediate G1
arrest via CDK inhibition, yet lower levels have no impact on
G1 progression, and the ubiquitin ligases CRL4Cdt2 and SCFSkp2
couple to degrade p21 prior to the G1/S transition.
Mathematical modelling reveals that a bistable switch, created
by CRL4Cdt2, promotes irreversible S-phase entry by keeping p21
levels low, preventing premature S-phase exit upon DNA damage.
Thus, we characterize how p21 regulates the
proliferation-quiescence decision to maintain genomic
stability.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000660.
To cite BioModels Database, please use:
Chelliah V et al. BioModels: ten-year
anniversary. Nucl. Acids Res. 2015, 43(Database
issue):D542-8.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Quiescent hematopoietic stem cells (HSCs) are prone to mutagenesis, and accumulation of mutations can result in hematological malignancies. The mechanisms through which HSCs prevent such detrimental accumulation, however, are unclear. Here, we show that Aspp1 coordinates with p53 to maintain the genomic integrity of the HSC pool. Aspp1 is preferentially expressed in HSCs and restricts HSC pool size by attenuating self-renewal under steady state conditions. After genotoxic stress, Aspp1 promotes HSC cycling and induces p53-dependent apoptosis in cells with persistent DNA damage foci. Beyond these p53-dependent functions, Aspp1 attenuates HSC self-renewal and accumulation of DNA damage in p53-null HSCs. Consequently, concomitant loss of Aspp1 and p53 leads to the development of hematological malignancies, especially T-cell leukemia and lymphoma. Together, these data highlights coordination between Aspp1 and p53 in regulating HSC self-renewal and DNA damage tolerance, and suggest that HSCs possess specific mechanisms that prevent accumulation of mutations and malignant transformation.
Project description:Heldt2018 - Proliferation-quiescence decision
in response to DNA damage
This model is described in the article:
A comprehensive model for
the proliferation-quiescence decision in response to endogenous
DNA damage in human cells.
Heldt FS, Barr AR, Cooper S, Bakal
C, Novák B.
Proc. Natl. Acad. Sci. U.S.A. 2018 Feb;
:
Abstract:
Human cells that suffer mild DNA damage can enter a
reversible state of growth arrest known as quiescence. This
decision to temporarily exit the cell cycle is essential to
prevent the propagation of mutations, and most cancer cells
harbor defects in the underlying control system. Here we
present a mechanistic mathematical model to study the
proliferation-quiescence decision in nontransformed human
cells. We show that two bistable switches, the restriction
point (RP) and the G1/S transition, mediate this decision by
integrating DNA damage and mitogen signals. In particular, our
data suggest that the cyclin-dependent kinase inhibitor p21
(Cip1/Waf1), which is expressed in response to DNA damage,
promotes quiescence by blocking positive feedback loops that
facilitate G1 progression downstream of serum stimulation.
Intriguingly, cells exploit bistability in the RP to convert
graded p21 and mitogen signals into an all-or-nothing
cell-cycle response. The same mechanism creates a window of
opportunity where G1 cells that have passed the RP can revert
to quiescence if exposed to DNA damage. We present experimental
evidence that cells gradually lose this ability to revert to
quiescence as they progress through G1 and that the onset of
rapid p21 degradation at the G1/S transition prevents this
response altogether, insulating S phase from mild, endogenous
DNA damage. Thus, two bistable switches conspire in the early
cell cycle to provide both sensitivity and robustness to
external stimuli.
This model is hosted on
BioModels Database
and identified by:
MODEL1703030000.
To cite BioModels Database, please use:
Chelliah V et al. BioModels: ten-year
anniversary. Nucl. Acids Res. 2015, 43(Database
issue):D542-8.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Hematopoietic stem cell (HSC) aging underlies many age-related hematopoietic disorders. Accumulation of DNA damage is a hallmark of HSC aging. Wild-type p53-induced phosphatase 1 (Wip1) is a homeostatic regulator of DNA damage response. We used microarrays to detail the global programme of gene expression in Wip1 KO HSC
Project description:Various modes of DNA repair counteract genotoxic DNA double-strand breaks (DSBs) to maintain genome stability. Recent findings suggest that the human DNA damage response (DDR) utilises damage-induced small RNA for efficient repair of DSBs. However, production and processing of RNA is poorly understood. Here we show that localised induction of DSBs triggers phosphorylation of RNA polymerase II (RNAPII) on carboxy-terminal domain (CTD) residue tyrosine-1 in an Mre11-Rad50-Nbs1 (MRN) complex-dependent manner. CTD Tyr1-phosphorylated RNAPII synthetises, strand-specific, damage-responsive transcripts (DARTs). DART synthesis occurs via formation of transient RNA-DNA hybrid (R-loop) intermediates. Impaired R-loop formation attenuates DART synthesis, impairs recruitment of repair factors and delays the DDR. Collectively, we provide mechanistic insight in RNA-dependent DSB repair.
Project description:Hematopoietic stem cell (HSC) aging underlies many age-related hematopoietic disorders. Accumulation of DNA damage is a hallmark of HSC aging. Wild-type p53-induced phosphatase 1 (Wip1) is a homeostatic regulator of DNA damage response. We used microarrays to detail the global programme of gene expression in Wip1 KO HSC Wild-type p53-induced phosphatase 1 (Wip1) knockout HSC and Wild type HSC were selected for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Targetted metabolomics in U2OS PRDX1 WT and PRDX1-/- While cellular metabolism impacts the DNA damage response, a systematic understanding of the metabolic requirements that are crucial for DNA damage repair has yet to be achieved. Here, we investigate the metabolic enzymes and processes that are essential when cells are exposed to DNA damage. By integrating functional genomics with chromatin proteomics and metabolomics, we provide a detailed description of the interplay between cellular metabolism and the DNA damage response. Subsequent analysis identified Peroxiredoxin 1, PRDX1, as fundamental for DNA damage repair. During the DNA damage response, PRDX1 translocates to the nucleus where it is required to reduce DNA damage-induced nuclear reactive oxygen species levels. Moreover, PRDX1 controls aspartate availability, which is required for the DNA damage repair-induced upregulation of de novo nucleotide synthesis. Loss of PRDX1 leads to an impairment in the clearance of γΗ2ΑΧ nuclear foci, accumulation of replicative stress and cell proliferation defects, thus revealing a crucial role for PRDX1 as a DNA damage surveillance factor.
Project description:Unrepaired DNA damage contributes to brain aging and neurodegenerative diseases. However, the factors stimulating DNA repair activity to stave off age-associated functional decline remain obscure. Here, we show that histone deacetylase 1 (HDAC1) modulates DNA repair in the aging brain via targeting OGG1 of the base excision repair pathway. Mice deficient in HDAC1 display age-associated accumulation of DNA damage in the brain and cognitive impairment. HDAC1 interacts with and positively stimulates OGG1, a DNA glycosylase that primarily acts on 8-oxoguanine (8-oxoG), a type of oxidative DNA damage associated with transcriptional repression. Loss of HDAC1 leads to impaired OGG1 activity, 8-oxoG accumulation at the promoters of a subset of genes critical for brain function, and transcriptional repression. Moreover, we observe elevated 8-oxoG lesions along with reduced HDAC1 activity and downregulation of a similar set genes in the 5XFAD mouse model of Alzheimer’s disease (AD). Notably, pharmacological activation of HDAC1 confers protection against the deleterious effects of 8-oxoG lesions in the brains of aged wild-type and 5XFAD mice. Our work uncovers an important role for HDAC1 in the repair of 8-oxoG lesions and highlights HDAC1 activation as a novel therapeutic strategy to counter functional decline during brain aging and neurodegeneration.
Project description:Upon DNA damage, the DNA damage response (DDR) elicits a complex signaling cascade, which includes the induction of multiple non-coding RNA species. Recently long non-coding RNAs (lncRNAs) have been shown to contribute to DDR by regulating gene expression. However, very little is known about the role that lncRNAs play in regulating DNA Repair. Using a genome-wide microarray screen we identified a novel ubiquitously expressed lncRNA, DDSR1 (DNA damage-sensitive RNA 1), which is induced upon DNA damage by several DNA double-strand break (DSB) agents. DDSR1 induction upon DNA damage is dependent on the ATM-NF-kB pathway but p53 independent. However, DDSR1 acts in the p53 network by negatively regulating p53 mediated gene expression. Loss of DDSR1 impairs cell proliferation, DDR signaling and reduces DNA repair capacity by homologous recombination (HR). The HR defect upon DDSR1 knockdown is due to reduced end resection caused by aberrant BRCA1 and RAP80 accumulation at DSB sites. In line with dual role of DDSR1 in gene regulation and HR, DDSR1 interacts with hnRNPUL1, an RNA-binding protein involved in transcription and HR. Our results reveal a previously unknown lncRNA involved in regulation of DDR by contributing to gene regulation and DNA repair by HR. Our findings highlight the importance of DDSR1 in maintaining genome stability and suggest that the DDR is even more complex than currently assumed. We used microarrays to identify gene expression changes upon DDSR1 knockdown