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Schultz, Niklas
Alternative names
Publications (10 of 34) Show all publications
Al-Ubaidi, F. L. T., Schultz, N., Egevad, L., Granfors, T. & Helleday, T. (2012). CASTRATION THERAPY OF PROSTATE CANCER RESULTS IN DOWNREGULATION OF HIF-1 alpha LEVELS. International Journal of Radiation Oncology, Biology, Physics, 82(3), 1243-1248
Open this publication in new window or tab >>CASTRATION THERAPY OF PROSTATE CANCER RESULTS IN DOWNREGULATION OF HIF-1 alpha LEVELS
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2012 (English)In: International Journal of Radiation Oncology, Biology, Physics, ISSN 0360-3016, E-ISSN 1879-355X, Vol. 82, no 3, p. 1243-1248Article in journal (Refereed) Published
Abstract [en]

Background and Purpose: Neoadjuvant androgen deprivation in combination with radiotherapy of prostate cancer is used to improve radioresponsiveness and local tumor control. Currently, the underlying mechanism is not well understood. Because hypoxia causes resistance to radiotherapy, we wanted to test whether castration affects the degree of hypoxia in prostate cancer. Methods and Materials: In 14 patients with locally advanced prostate cancer, six to 12 prostatic needle core biopsy specimens were taken prior to castration therapy. Bilateral orchidectomy was performed in 7 patients, and 7 were treated with a GnRH-agonist (leuprorelin). After castrationm two to four prostatic core biopsy specimens were taken, and the level of hypoxia-inducible factor-1 alpha (HIF-1 alpha) in cancer was determined by immunofluorescence. Results: Among biopsy specimens taken before castration, strong HIF-1 alpha expression (mean intensity above 30) was shown in 5 patients, weak expression (mean intensity 10-30) in 3 patients, and background levels of HIF-1 alpha (mean intensity 0-10) in 6 patients. Downregulation of HIF-1 alpha expression after castration was observed in all 5 patients with strong HIF-1 alpha precastration expression. HIF-1 alpha expression was also reduced in 2 of 3 patients with weak HIF-1 alpha precastration expression. Conclusions: Our data suggest that neoadjuvant castration decreases tumor cell hypoxia in prostate cancer, which may explain increased radiosensitivity after castration.

Keywords
Hypoxia-inducible factor, HIF-1 alpha, Prostate cancer
National Category
Urology and Nephrology
Identifiers
urn:nbn:se:su:diva-76984 (URN)10.1016/j.ijrobp.2011.10.038 (DOI)000300423500064 ()
Note

5

Available from: 2012-06-05 Created: 2012-05-28 Last updated: 2024-02-09Bibliographically approved
Ström, C. E., Mortusewicz, O., Finch, D., Parsons, J. L., Lagerqvist, A., Johansson, F., . . . Helleday, T. (2011). CK2 phosphorylation of XRCC1 facilitates dissociation from DNA and single-strand break formation during base excision repair. DNA Repair, 10(9), 961-969
Open this publication in new window or tab >>CK2 phosphorylation of XRCC1 facilitates dissociation from DNA and single-strand break formation during base excision repair
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2011 (English)In: DNA Repair, ISSN 1568-7864, E-ISSN 1568-7856, Vol. 10, no 9, p. 961-969Article in journal (Refereed) Published
Abstract [en]

CK2 phosphorylates the scaffold protein XRCC1, which is required for efficient DNA single-strand break (SSB) repair. Here, we express an XRCC1 protein (XRCC1(ckm)) that cannot be phosphorylated by CK2 in XRCC1 mutated EM9 cells and show that the role of this post-translational modification gives distinct phenotypes in SSB repair and base excision repair (BER). Interestingly, we find that fewer SSBs are formed during BER after treatment with the allcylating agent dimethyl sulfate (DMS) in EM9 cells expressing XRCC1(ckm) (CKM cells) or following inhibition with the CK2 inhibitor 2-dimethylamino-4,5,6,7tetrabromo-1H-benzimidazole (DMAT). We also show that XRCC1(ckm) protein has a higher affinity for DNA than wild type XRCC1 protein and resides in an immobile fraction on DNA, in particular after damage. We propose a model whereby the increased affinity for DNA sequesters XRCC1(ckm) and the repair enzymes associated with it, at the repair site, which retards kinetics of BER. In conclusion, our results indicate that phosphorylation of XRCC1 by CK2 facilitates the BER incision step, likely by promoting.

Keywords
CK2, XRCC1, Dimethyl sulfate, Mammalian cells, Base excision repair, Single-strand break, Chinese hamster ovary cells
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-67294 (URN)10.1016/j.dnarep.2011.07.004 (DOI)000295242600007 ()
Note
authorCount :10Available from: 2011-12-27 Created: 2011-12-27 Last updated: 2022-02-24Bibliographically approved
Stoimenov, I., Gottipati, P., Schultz, N. & Helleday, T. (2011). Transcription inhibition by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) causes DNA damage and triggers homologous recombination repair in mammalian cells. Mutation research, 706(1-2), 1-6
Open this publication in new window or tab >>Transcription inhibition by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) causes DNA damage and triggers homologous recombination repair in mammalian cells
2011 (English)In: Mutation research, ISSN 0027-5107, E-ISSN 1873-135X, Vol. 706, no 1-2, p. 1-6Article in journal (Refereed) Published
Abstract [en]

Transcription, replication and homologous recombination are intrinsically connected and it is well established that an increase of transcription is associated with an increase in homologous recombination. Here, we have studied how homologous recombination is affected during transcription inhibition by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), a compound that prevents activating phosphorylations of the RNA Pol II C-terminal domain. We identify that DRB triggers an increase in homologous recombination within the hprt gene as well as increasing RAD51 foci formation in mammalian cells. Furthermore, we find that DRB-induced transcriptional stress is associated with formation of the nuclear foci of the phosphorylated form of H2AX (γH2AX). We accounted that about 72% of RAD51 foci co-localized with the observed γH2AX foci. Interestingly, we find that XRCC3 mutated, homologous recombination defective cells are hypersensitive to the toxic effect of DRB and fail to form RAD51 foci. In conclusion, we show that DRB-induced transcription inhibition is associated with the formation of a lesion that triggers RAD51-dependent homologous recombination repair, required for survival under transcriptional stress.

Keywords
Homologous recombination, DRB, Transcription, DNA damage repair, Mammalian cells
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Genetics
Identifiers
urn:nbn:se:su:diva-54714 (URN)10.1016/j.mrfmmm.2010.10.012 (DOI)000287123600001 ()
Available from: 2011-02-14 Created: 2011-02-13 Last updated: 2022-02-24Bibliographically approved
Stoimenov, I., Schultz, N., Gottipati, P. & Helleday, T. (2011). Transcription Inhibition by DRB Potentiates Recombinational Repair of UV Lesions in Mammalian Cells. PLOS ONE, 6(5), e19492
Open this publication in new window or tab >>Transcription Inhibition by DRB Potentiates Recombinational Repair of UV Lesions in Mammalian Cells
2011 (English)In: PLOS ONE, E-ISSN 1932-6203, Vol. 6, no 5, p. e19492-Article in journal (Refereed) Published
Abstract [en]

Homologous recombination (HR) is intricately associated with replication, transcription and DNA repair in all organisms studied. However, the interplay between all these processes occurring simultaneously on the same DNA molecule is still poorly understood. Here, we study the interplay between transcription and HR during ultraviolet light (UV)-induced DNA damage in mammalian cells. Our results show that inhibition of transcription with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) increases the number of UV-induced DNA lesions (gamma H2AX, 53BP1 foci formation), which correlates with a decrease in the survival of wild type or nucleotide excision repair defective cells. Furthermore, we observe an increase in RAD51 foci formation, suggesting HR is triggered in response to an increase in UV-induced DSBs, while inhibiting transcription. Unexpectedly, we observe that DRB fails to sensitise HR defective cells to UV treatment. Thus, increased RAD51 foci formation correlates with increased cell death, suggesting the existence of a futile HR repair of UV-induced DSBs which is linked to transcription inhibition.

National Category
Biological Sciences
Identifiers
urn:nbn:se:su:diva-68119 (URN)10.1371/journal.pone.0019492 (DOI)000290256400015 ()
Note
authorCount :4Available from: 2012-01-03 Created: 2012-01-03 Last updated: 2022-02-24Bibliographically approved
Petermann, E., Orta, M. L., Issaeva, N., Schultz, N. & Helleday, T. (2010). Hydroxyurea-stalled replication forks become progressively inactivated and require two different RAD51-mediated pathways for restart and repair.. Molecular Cell, 37(4), 492-502
Open this publication in new window or tab >>Hydroxyurea-stalled replication forks become progressively inactivated and require two different RAD51-mediated pathways for restart and repair.
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2010 (English)In: Molecular Cell, ISSN 1097-2765, E-ISSN 1097-4164, Vol. 37, no 4, p. 492-502Article in journal (Refereed) Published
Abstract [en]

Faithful DNA replication is essential to all life. Hydroxyurea (HU) depletes the cells of dNTPs, which initially results in stalled replication forks that, after prolonged treatment, collapse into DSBs. Here, we report that stalled replication forks are efficiently restarted in a RAD51-dependent process that does not trigger homologous recombination (HR). The XRCC3 protein, which is required for RAD51 foci formation, is also required for replication restart of HU-stalled forks, suggesting that RAD51-mediated strand invasion supports fork restart. In contrast, replication forks collapsed by prolonged replication blocks do not restart, and global replication is rescued by new origin firing. We find that RAD51-dependent HR is triggered for repair of collapsed replication forks, without apparent restart. In conclusion, our data suggest that restart of stalled replication forks and HR repair of collapsed replication forks require two distinct RAD51-mediated pathways.

Identifiers
urn:nbn:se:su:diva-52955 (URN)10.1016/j.molcel.2010.01.021 (DOI)20188668 (PubMedID)
Available from: 2011-01-19 Created: 2011-01-19 Last updated: 2022-02-24Bibliographically approved
Waluk, D. P., Schultz, N. & Hunt, M. C. (2010). Identification of glycine N-acyltransferase-like 2 (GLYATL2) as a transferase that produces N-acyl glycines in humans.. The FASEB Journal, 24(8), 2795-2803
Open this publication in new window or tab >>Identification of glycine N-acyltransferase-like 2 (GLYATL2) as a transferase that produces N-acyl glycines in humans.
2010 (English)In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 24, no 8, p. 2795-2803Article in journal (Refereed) Published
Abstract [en]

The discovery of glycine conjugates of long-chain fatty acids (N-acyl glycines) in the brain and other non-neuronal tissues has led to the identification of an emerging class of bioactive lipids. The biological activities of N-acyl glycines include antinociceptive, anti-inflammatory and antiproliferative effects, and activation of G-protein-coupled receptors. However, despite the fact that N-acyl glycines are emerging as a distinct lipid signaling family, pathways for their production are not fully elucidated. Here we report on the characterization of human glycine N-acyltransferase-like 2 (hGLYATL2), a member of a gene family of 4 putative glycine conjugating enzymes, and show that it synthesizes various N-acyl glycines. Recombinantly expressed hGLYATL2 efficiently conjugated oleoyl-CoA, arachidonoyl-CoA, and other medium- and long-chain acyl-CoAs to glycine. The enzyme was specific for glycine as an acceptor molecule, and preferentially produced N-oleoyl glycine. The hGLYATL2 enzyme is localized to the endoplasmic reticulum, and the mRNA shows highest expression in salivary gland and trachea, but is also detected in spinal cord and skin fibroblasts. The expression pattern and the identification of high levels of N-acyl glycines in skin and lung may indicate a role for N-acyl glycines in barrier function/immune response and the potential role of hGLYATL2 in this regard is discussed.

Keywords
N-oleoyl glycine, N-arachidonoyl glycine, endocannabinoids, N-acyl amino acids, endoplasmic reticulum
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry; Molecular Cellbiology; Molecular Genetics
Identifiers
urn:nbn:se:su:diva-75625 (URN)10.1096/fj.09-148551 (DOI)
Funder
Swedish Research Council
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2022-02-24Bibliographically approved
Groth, P., Auslander, S., Majumder, M. M., Schultz, N., Johansson, F., Petermann, E. & Helleday, T. (2010). Methylated DNA Causes a Physical Block to Replication Forks Independently of Damage Signalling, O-6-Methylguanine or DNA Single-Strand Breaks and Results in DNA Damage. Journal of Molecular Biology, 402(1), 70-82
Open this publication in new window or tab >>Methylated DNA Causes a Physical Block to Replication Forks Independently of Damage Signalling, O-6-Methylguanine or DNA Single-Strand Breaks and Results in DNA Damage
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2010 (English)In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 402, no 1, p. 70-82Article in journal (Refereed) Published
Abstract [en]

Even though DNA alkylating agents have been used for many decades in the treatment of cancer, it remains unclear what happens when replication forks encounter alkylated DNA. Here, we used the DNA fibre assay to study the impact of alkylating agents on replication fork progression. We found that the alkylator methyl methanesulfonate (MMS) inhibits replication elongation in a manner that is dose dependent and related to the overall alkylation grade. Replication forks seem to be completely blocked as no nucleotide incorporation can be detected following 1 h of MMS treatment. A high dose of 5 mM caffeine, inhibiting most DNA damage signalling, decreases replication rates overall but does not reverse MMS-induced replication inhibition, showing that the replication block is independent of DNA damage signalling. Furthermore, the block of replication fork progression does not correlate with the level of DNA single-strand breaks. Overexpression of O-6-methylguanine (O6meG)-DNA methyltransferase protein, responsible for removing the most toxic alkylation, O6meG, did not affect replication elongation following exposure to N-methyl-M-nitro-N-nitrosoguanidine. This demonstrates that O6meG lesions are efficiently bypassed in mammalian cells. In addition, we find that MMS-induced gamma H2AX foci co-localise with 53BP1 foci and newly replicated areas, suggesting that DNA double-strand breaks are formed at MMS-blocked replication forks. Altogether, our data suggest that N-alkylations formed during exposure to alkylating agents physically block replication fork elongation in mammalian cells, causing formation of replication-associated DNA lesions, likely double-strand breaks.

Keywords
N-methyl-N '-nitro-N-nitrosoguanidine, methyl methanesulfonate, mammalian cells, replication fork elongation, double-strand breaks
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-52234 (URN)10.1016/j.jmb.2010.07.010 (DOI)000282074500007 ()
Note
authorCount :7Available from: 2011-01-13 Created: 2011-01-13 Last updated: 2022-02-24Bibliographically approved
Gottipati, P., Vischioni, B., Schultz, N., Solomons, J., Bryant, H. E., Djureinovic, T., . . . Helleday, T. (2010). Poly(ADP-Ribose) Polymerase Is Hyperactivated in Homologous Recombination-Defective Cells. Cancer Research, 70(13), 5389-5398
Open this publication in new window or tab >>Poly(ADP-Ribose) Polymerase Is Hyperactivated in Homologous Recombination-Defective Cells
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2010 (English)In: Cancer Research, ISSN 0008-5472, E-ISSN 1538-7445, Vol. 70, no 13, p. 5389-5398Article in journal (Refereed) Published
Abstract [en]

Poly(ADP-ribose) (PAR) polymerase 1 (PARP1) is activated by DNA single-strand breaks (SSB) or at stalled replication forks to facilitate DNA repair. Inhibitors of PARP efficiently kill breast, ovarian, or prostate tumors in patients carrying hereditary mutations in the homologous recombination (HR) genes BRCA1 or BRCA2 through synthetic lethality. Here, we surprisingly show that PARP1 is hyperactivated in replicating BRCA2-defective cells. PARP1 hyperactivation is explained by the defect in HR as shRNA depletion of RAD54, RAD52, BLM, WRN, and XRCC3 proteins, which we here show are all essential for efficient HR and also caused PARP hyperactivation and correlated with an increased sensitivity to PARP inhibitors. BRCA2-defective cells were not found to have increased levels of SSBs, and PAR polymers formed in HR-defective cells do not colocalize to replication protein A or gamma H2AX, excluding the possibility that PARP hyperactivity is due to increased SSB repair or PARP induced at damaged replication forks. Resistance to PARP inhibitors can occur through genetic reversion in the BRCA2 gene. Here, we report that PARP inhibitor-resistant BRCA2-mutant cells revert back to normal levels of PARP activity. We speculate that the reason for the sensitivity of HR-defective cells to PARP inhibitors is related to the hyperactivated PARP1 in these cells. Furthermore, the presence of PAR polymers can be used to identify HR-defective cells that are sensitive to PARP inhibitors, which may be potential biomarkers. Cancer Res; 70(13); 5389-98. (C) 2010 AACR.

National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-50302 (URN)10.1158/0008-5472.CAN-09-4716 (DOI)000279396800021 ()
Note
authorCount :10Available from: 2010-12-22 Created: 2010-12-22 Last updated: 2022-02-24Bibliographically approved
Bryant, H. E., Petermann, E., Schultz, N., Jemth, A.-S., Loseva, O., Issaeva, N., . . . Helleday, T. (2009). PARP is activated at stalled forks to mediate Mre11-dependent replication restart and recombination.. The EMBO journal, 28(17), 2601-15
Open this publication in new window or tab >>PARP is activated at stalled forks to mediate Mre11-dependent replication restart and recombination.
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2009 (English)In: The EMBO journal, ISSN 1460-2075, Vol. 28, no 17, p. 2601-15Article in journal (Refereed) Published
Abstract [en]

If replication forks are perturbed, a multifaceted response including several DNA repair and cell cycle checkpoint pathways is activated to ensure faithful DNA replication. Here, we show that poly(ADP-ribose) polymerase 1 (PARP1) binds to and is activated by stalled replication forks that contain small gaps. PARP1 collaborates with Mre11 to promote replication fork restart after release from replication blocks, most likely by recruiting Mre11 to the replication fork to promote resection of DNA. Both PARP1 and PARP2 are required for hydroxyurea-induced homologous recombination to promote cell survival after replication blocks. Together, our data suggest that PARP1 and PARP2 detect disrupted replication forks and attract Mre11 for end processing that is required for subsequent recombination repair and restart of replication forks.

Identifiers
urn:nbn:se:su:diva-32006 (URN)10.1038/emboj.2009.206 (DOI)000269494200010 ()19629035 (PubMedID)
Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2022-02-25Bibliographically approved
Al-Minawi, A. Z., Lee, Y.-F., Håkansson, D., Johansson, F., Lundin, C., Saleh-Gohari, N., . . . Helleday, T. (2009). The ERCC1/XPF endonuclease is required for completion of homologous recombination at DNA replication forks stalled by inter-strand cross-links. Nucleic Acids Research, 37(19), 6400-6413
Open this publication in new window or tab >>The ERCC1/XPF endonuclease is required for completion of homologous recombination at DNA replication forks stalled by inter-strand cross-links
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2009 (English)In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 37, no 19, p. 6400-6413Article in journal (Refereed) Published
Abstract [en]

Both the ERCC1-XPF complex and the proteins involved in homoIogous recombination (HR) have critical roles in inter-strand cross-link (ICL) repair. Here, we report that mitomycin C-induced lesions inhibit replication fork elongation. Furthermore, mitomycin C-induced DNA double-strand breaks (DSBs) are the result of the collapse of ICL-stalled replication forks. These are not formed through replication run off, as we show that mitomycin C or cisplatin-induced DNA lesions are not incised by global genome nucleotide excision repair (GGR). We also suggest that ICL-lesion repair is initiated either by replication or transcription, as the GGR does not incise ICL-lesions. Furthermore, we report that RAD51 foci are induced by cisplatin or mitomycin C independently of ERCC1, but that mitomycin C-induced HR measured in a reporter construct is impaired in ERCC1-defective cells. These data suggest that ERCC1-XPF plays a role in completion of HR in ICL repair. We also find no additional sensitivity to cisplatin by siRNA co-depletion of XRCC3 and ERCC1, showing that the two proteins act on the same pathway to promote survival.

National Category
Biochemistry and Molecular Biology
Research subject
Molecular Genetics
Identifiers
urn:nbn:se:su:diva-32005 (URN)10.1093/nar/gkp705 (DOI)000271389900010 ()19713438 (PubMedID)
Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2022-02-25Bibliographically approved
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