Checkpoint-dependent RNR induction promotes fork restart after replicative stress

Morafraile, Esther Cabañas; Diffley, John F.X.; Tercero, José Antonio; Segurado, Mónica

doi:10.1038/srep07886

Cited by 17 publications

(14 citation statements)

References 53 publications

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“…1b) [52]. Importantly, combined over-expression of the RNR2 and RNR4 genes partially suppresses the HU hyper-sensitivity of rad53 mutant cells, supporting the idea that S-phase checkpoint-dependent RNR up-regulation contributes to cell survival of rad53 cells under conditions that inhibit RNR [53]. Up-regulation of the cellular pool of dNTPs through the degradation of RNR inhibitors, increased transcription of the RNR genes, and subcellular re-localization of the RNR subunits, are also potent cellular responses to DNA replication inhibition in mammalian cells where the ATR–CHK1 kinase pathway induces the accumulation of the RRM2 (Ribonucleoside-diphosphate Reductase subunit M 2) subunit of RNR following replication stress (Fig.…”

Section: Replication Fork-extrinsic S-phase Checkpoint-dependent Regumentioning

confidence: 81%

S-phase checkpoint regulations that preserve replication and chromosome integrity upon dNTP depletion

Giannattasio

Branzei

2017

Cell. Mol. Life Sci.

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DNA replication stress, an important source of genomic instability, arises upon different types of DNA replication perturbations, including those that stall replication fork progression. Inhibitors of the cellular pool of deoxynucleotide triphosphates (dNTPs) slow down DNA synthesis throughout the genome. Following depletion of dNTPs, the highly conserved replication checkpoint kinase pathway, also known as the S-phase checkpoint, preserves the functionality and structure of stalled DNA replication forks and prevents chromosome fragmentation. The underlying mechanisms involve pathways extrinsic to replication forks, such as those involving regulation of the ribonucleotide reductase activity, the temporal program of origin firing, and cell cycle transitions. In addition, the S-phase checkpoint modulates the function of replisome components to promote replication integrity. This review summarizes the various functions of the replication checkpoint in promoting replication fork stability and genome integrity in the face of replication stress caused by dNTP depletion.

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Section: Replication Fork-extrinsic S-phase Checkpoint-dependent Regumentioning

confidence: 81%

S-phase checkpoint regulations that preserve replication and chromosome integrity upon dNTP depletion

Giannattasio

Branzei

2017

Cell. Mol. Life Sci.

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“…Increasing RNR activity in progeroid mice alleviates the severity of the premature aging phenotype (59). RNR also has been observed to promote fork restart after replicative stress (60). Thus, the accumulation of progerin in these aging HGPS cells has multiple effects in regulating DNA metabolism and altering progression through the cell cycle.…”

Section: Discussionmentioning

confidence: 99%

Progerin sequestration of PCNA promotes replication fork collapse and mislocalization of XPA in laminopathy‐related progeroid syndromes

et al. 2017

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Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder that is caused by a point mutation in the gene, resulting in production of a truncated farnesylated-prelamin A protein (progerin). We previously reported that XPA mislocalized to the progerin-induced DNA double-strand break (DSB) sites, blocking DSB repair, which led to DSB accumulation, DNA damage responses, and early replication arrest in HGPS. In this study, the XPA mislocalization to DSBs occurred at stalled or collapsed replication forks, concurrent with a significant loss of PCNA at the forks, whereas PCNA efficiently bound to progerin. This PCNA sequestration likely exposed ds-ssDNA junctions at replication forks for XPA binding. Depletion of XPA or progerin each significantly restored PCNA at replication forks. Our results suggest that although PCNA is much more competitive than XPA in binding replication forks, PCNA sequestration by progerin may shift the equilibrium to favor XPA binding. Furthermore, we demonstrated that progerin-induced apoptosis could be rescued by XPA, suggesting that XPA-replication fork binding may prevent apoptosis in HGPS cells. Our results propose a mechanism for progerin-induced genome instability and accelerated replicative senescence in HGPS.-Hilton, B. A., Liu, J., Cartwright, B. M., Liu, Y., Breitman, M., Wang, Y., Jones, R., Tang, H., Rusinol, A., Musich, P. R., Zou, Y. Progerin sequestration of PCNA promotes replication fork collapse and mislocalization of XPA in laminopathy-related progeroid syndromes.

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“…This may be explained by replication fork collapses in rnr1Δ crt1Δ est2Δ mutants that become restarted by HDR, leading to the premature formation of survivors in the absence of both telomerase and Rnr1. Indeed, a checkpoint-dependent induction of RNR has recently been shown to promote the restart of stalled replication forks in response to replicative stress [ 55 ]. The fact that telomerase-negative rnr1 Δ crt1 Δ mutants are capable to efficiently elongate their telomeres by HDR further indicates that telomerase-dependent telomere elongation is more sensitive to a loss of Rnr1 activity than HDR-mediated elongation mechanisms.…”

Section: Discussionmentioning

confidence: 99%

Rnr1, but not Rnr3, facilitates the sustained telomerase-dependent elongation of telomeres

et al. 2017

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Ribonucleotide reductase (RNR) provides the precursors for the generation of dNTPs, which are required for DNA synthesis and repair. Here, we investigated the function of the major RNR subunits Rnr1 and Rnr3 in telomere elongation in budding yeast. We show that Rnr1 is essential for the sustained elongation of short telomeres by telomerase. In the absence of Rnr1, cells harbor very short, but functional, telomeres, which cannot become elongated by increased telomerase activity or by tethering of telomerase to telomeres. Furthermore, we demonstrate that Rnr1 function is critical to prevent an early onset of replicative senescence and premature survivor formation in telomerase-negative cells but dispensable for telomere elongation by Homology-Directed-Repair. Our results suggest that telomerase has a "basal activity" mode that is sufficient to compensate for the “end-replication-problem” and does not require the presence of Rnr1 and a different "sustained activity" mode necessary for the elongation of short telomeres, which requires an upregulation of dNTP levels and dGTP ratios specifically through Rnr1 function. By analyzing telomere length and dNTP levels in different mutants showing changes in RNR complex composition and activity we provide evidence that the Mec1ATR checkpoint protein promotes telomere elongation by increasing both dNTP levels and dGTP ratios through Rnr1 upregulation in a mechanism that cannot be replaced by its homolog Rnr3.

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Checkpoint-dependent RNR induction promotes fork restart after replicative stress

Cited by 17 publications

References 53 publications

S-phase checkpoint regulations that preserve replication and chromosome integrity upon dNTP depletion

S-phase checkpoint regulations that preserve replication and chromosome integrity upon dNTP depletion

Progerin sequestration of PCNA promotes replication fork collapse and mislocalization of XPA in laminopathy‐related progeroid syndromes

Rnr1, but not Rnr3, facilitates the sustained telomerase-dependent elongation of telomeres

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