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Liew LP, Lim ZY, Cohen M, Kong Z, Marjavaara L, Chabes A, Bell SD. Hydroxyurea-Mediated Cytotoxicity Without Inhibition of Ribonucleotide Reductase. Cell Rep 2017; 17:1657-1670. [PMID: 27806303 PMCID: PMC5134839 DOI: 10.1016/j.celrep.2016.10.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 07/29/2016] [Accepted: 10/07/2016] [Indexed: 11/30/2022] Open
Abstract
In many organisms, hydroxyurea (HU) inhibits class I ribonucleotide reductase, leading to lowered cellular pools of deoxyribonucleoside triphosphates. The reduced levels for DNA precursors is believed to cause replication fork stalling. Upon treatment of the hyperthermophilic archaeon Sulfolobus solfataricus with HU, we observe dose-dependent cell cycle arrest, accumulation of DNA double-strand breaks, stalled replication forks, and elevated levels of recombination structures. However, Sulfolobus has a HU-insensitive class II ribonucleotide reductase, and we reveal that HU treatment does not significantly impact cellular DNA precursor pools. Profiling of protein and transcript levels reveals modulation of a specific subset of replication initiation and cell division genes. Notably, the selective loss of the regulatory subunit of the primase correlates with cessation of replication initiation and stalling of replication forks. Furthermore, we find evidence for a detoxification response induced by HU treatment. Sulfolobus has a HU-insensitive class II ribonucleotide reductase HU impairs DNA replication and is toxic to Sulfolobus cells HU treatment leads to selective loss of the regulatory subunit of DNA primase
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Affiliation(s)
- Li Phing Liew
- Sir William Dunn School of Pathology, South Parks Road, Oxford OX1 3RE, UK
| | - Zun Yi Lim
- Department of Molecular and Cellular Biochemistry, Indiana University, Simon Hall MSB, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Matan Cohen
- Department of Biology, Indiana University, Simon Hall MSB, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Ziqing Kong
- Department of Medical Biochemistry and Biophysics, Umeå University, SE 90197 Umeå, Sweden
| | - Lisette Marjavaara
- Department of Medical Biochemistry and Biophysics, Umeå University, SE 90197 Umeå, Sweden
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, SE 90197 Umeå, Sweden; Laboratory for Molecular Infection Medicine Sweden, Umeå University, SE 90197 Umeå, Sweden
| | - Stephen D Bell
- Department of Molecular and Cellular Biochemistry, Indiana University, Simon Hall MSB, 212 South Hawthorne Drive, Bloomington, IN 47405, USA; Department of Biology, Indiana University, Simon Hall MSB, 212 South Hawthorne Drive, Bloomington, IN 47405, USA.
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Replication fork collapse and genome instability in a deoxycytidylate deaminase mutant. Mol Cell Biol 2012; 32:4445-54. [PMID: 22927644 DOI: 10.1128/mcb.01062-12] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Ribonucleotide reductase (RNR) and deoxycytidylate deaminase (dCMP deaminase) are pivotal allosteric enzymes required to maintain adequate pools of deoxyribonucleoside triphosphates (dNTPs) for DNA synthesis and repair. Whereas RNR inhibition slows DNA replication and activates checkpoint responses, the effect of dCMP deaminase deficiency is largely unknown. Here, we report that deleting the Schizosaccharomyces pombe dcd1(+) dCMP deaminase gene (SPBC2G2.13c) increases dCTP ∼30-fold and decreases dTTP ∼4-fold. In contrast to the robust growth of a Saccharomyces cerevisiae dcd1Δ mutant, fission yeast dcd1Δ cells delay cell cycle progression in early S phase and are sensitive to multiple DNA-damaging agents, indicating impaired DNA replication and repair. DNA content profiling of dcd1Δ cells differs from an RNR-deficient mutant. Dcd1 deficiency activates genome integrity checkpoints enforced by Rad3 (ATR), Cds1 (Chk2), and Chk1 and creates critical requirements for proteins involved in recovery from replication fork collapse, including the γH2AX-binding protein Brc1 and Mus81 Holliday junction resolvase. These effects correlate with increased nuclear foci of the single-stranded DNA binding protein RPA and the homologous recombination repair protein Rad52. Moreover, Brc1 suppresses spontaneous mutagenesis in dcd1Δ cells. We propose that replication forks stall and collapse in dcd1Δ cells, burdening DNA damage and checkpoint responses to maintain genome integrity.
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Interplay of DNA repair pathways controls methylation damage toxicity in Saccharomyces cerevisiae. Genetics 2008; 179:1835-44. [PMID: 18579505 DOI: 10.1534/genetics.108.089979] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Methylating agents of S(N)1 type are widely used in cancer chemotherapy, but their mode of action is poorly understood. In particular, it is unclear how the primary cytotoxic lesion, O(6)-methylguanine ((Me)G), causes cell death. One hypothesis stipulates that binding of mismatch repair (MMR) proteins to (Me)G/T mispairs arising during DNA replication triggers cell-cycle arrest and cell death. An alternative hypothesis posits that (Me)G cytotoxicity is linked to futile processing of (Me)G-containing base pairs by the MMR system. In this study, we provide compelling genetic evidence in support of the latter hypothesis. Treatment of 4644 deletion mutants of Saccharomyces cerevisiae with the prototypic S(N)1-type methylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) identified MMR as the only pathway that sensitizes cells to MNNG. In contrast, homologous recombination (HR), postreplicative repair, DNA helicases, and chromatin maintenance factors protect yeast cells against the cytotoxicity of this chemical. Notably, DNA damage signaling proteins played a protective rather than sensitizing role in the MNNG response. Taken together, this evidence demonstrates that (Me)G-containing lesions in yeast must be processed to be cytotoxic.
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