| 1. |
- Forey, Romain, et al.
(författare)
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Mec1 Is Activated at the Onset of Normal S Phase by Low-dNTP Pools Impeding DNA Replication
- 2020
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Ingår i: Molecular Cell. - : Elsevier. - 1097-2765 .- 1097-4164. ; 78:3, s. 496-410.e4
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Tidskriftsartikel (refereegranskat)abstract
- The Mec1 and Rad53 kinases play a central role during acute replication stress in budding yeast. They are also essential for viability in normal growth conditions, but the signal that activates the Mec1-Rad53 pathway in the absence of exogenous insults is currently unknown. Here, we show that this pathway is active at the onset of normal S phase because deoxyribonucleotide triphosphate (dNTP) levels present in G1 phase may not be sufficient to support processive DNA synthesis and impede DNA replication. This activation can be suppressed experimentally by increasing dNTP levels in G1 phase. Moreover, we show that unchallenged cells entering S phase in the absence of Rad53 undergo irreversible fork collapse and mitotic catastrophe. Together, these data indicate that cells use suboptimal dNTP pools to detect the onset of DNA replication and activate the Mec1-Rad53 pathway, which in turn maintains functional forks and triggers dNTP synthesis, allowing the completion of DNA replication.
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| 2. |
- Gan, Haiyun, et al.
(författare)
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Checkpoint Kinase Rad53 Couples Leading- and Lagging-Strand DNA Synthesis under Replication Stress
- 2017
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Ingår i: Molecular Cell. - : Elsevier. - 1097-2765 .- 1097-4164. ; 68:2, s. 446-455
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Tidskriftsartikel (refereegranskat)abstract
- The checkpoint kinase Rad53 is activated during replication stress to prevent fork collapse, an essential but poorly understood process. Here we show that Rad53 couples leading- and lagging-strand synthesis under replication stress. In rad53-1 cells stressed by dNTP depletion, the replicative DNA helicase, MCM, and the leading-strand DNA polymerase, Pol ε, move beyond the site of DNA synthesis, likely unwinding template DNA. Remarkably, DNA synthesis progresses further along the lagging strand than the leading strand, resulting in the exposure of long stretches of single-stranded leading-strand template. The asymmetric DNA synthesis in rad53-1 cells is suppressed by elevated levels of dNTPs in vivo, and the activity of Pol ε is compromised more than lagging-strand polymerase Pol δ at low dNTP concentrations in vitro. Therefore, we propose that Rad53 prevents the generation of excessive ssDNA under replication stress by coordinating DNA unwinding with synthesis of both strands.
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| 3. |
- Nicholls, Thomas J., et al.
(författare)
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Dinucleotide Degradation by REXO2 Maintains Promoter Specificity in Mammalian Mitochondria
- 2019
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-2765 .- 1097-4164. ; 76:5, s. 784-
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Tidskriftsartikel (refereegranskat)abstract
- Oligoribonucleases are conserved enzymes that degrade short RNA molecules of up to 5 nt in length and are assumed to constitute the final stage of RNA turnover. Here we demonstrate that REXO2 is a specialized dinucleotide-degrading enzyme that shows no preference between RNA and DNA dinucleotide substrates. A heart- and skeletal-muscle-specific knockout mouse displays elevated dinucleotide levels and alterations in gene expression patterns indicative of aberrant dinucleotide-primed transcription initiation. We find that dinucleotides act as potent stimulators of mitochondrial transcription initiation in vitro. Our data demonstrate that increased levels of dinucleotides can be used to initiate transcription, leading to an increase in transcription levels from both mitochondrial promoters and other, nonspecific sequence elements in mitochondrial DNA. Efficient RNA turnover by REXO2 is thus required to maintain promoter specificity and proper regulation of transcription in mammalian mitochondria.
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