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Bossaert M, Moreno A, Peixoto A, Pillaire MJ, Chanut P, Frit P, Calsou P, Loparo JJ, Britton S. Identification of the main barriers to Ku accumulation in chromatin. bioRxiv 2024:2024.01.03.574002. [PMID: 38260538 PMCID: PMC10802386 DOI: 10.1101/2024.01.03.574002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Repair of DNA double strand breaks by the non-homologous end-joining pathway is initiated by the binding of Ku to DNA ends. Given its high affinity for ends, multiple Ku proteins load onto linear DNAs in vitro. However, in cells, Ku loading is limited to ~1-2 molecules per DNA end. The mechanisms enforcing this limit are currently unknown. Here we show that the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs), but not its protein kinase activity, is required to prevent excessive Ku entry into chromatin. Ku accumulation is further restricted by two mechanisms: a neddylation/FBXL12-dependent process which actively removes loaded Ku molecules throughout the cell cycle and a CtIP/ATM-dependent mechanism which operates in S-phase. Finally, we demonstrate that the misregulation of Ku loading leads to impaired transcription in the vicinity of DNA ends. Together our data shed light on the multiple layers of coordinated mechanisms operating to prevent Ku from invading chromatin and interfering with other DNA transactions.
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Affiliation(s)
- Madeleine Bossaert
- Institut de Pharmacologie et Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Equipe labélisée la Ligue contre le Cancer 2018
| | - Andrew Moreno
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts 02115
| | - Antonio Peixoto
- Institut de Pharmacologie et Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Equipe labélisée la Ligue contre le Cancer 2018
| | - Marie-Jeanne Pillaire
- Institut de Pharmacologie et Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Equipe labélisée la Ligue contre le Cancer 2018
| | - Pauline Chanut
- Institut de Pharmacologie et Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Equipe labélisée la Ligue contre le Cancer 2018
| | - Philippe Frit
- Institut de Pharmacologie et Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Equipe labélisée la Ligue contre le Cancer 2018
| | - Patrick Calsou
- Institut de Pharmacologie et Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Equipe labélisée la Ligue contre le Cancer 2018
| | - Joseph John Loparo
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts 02115
| | - Sébastien Britton
- Institut de Pharmacologie et Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Equipe labélisée la Ligue contre le Cancer 2018
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Brunner A, Li Q, Fisicaro S, Kourtesakis A, Viiliäinen J, Johansson HJ, Pandey V, Mayank AK, Lehtiö J, Wohlschlegel JA, Spruck C, Rantala JK, Orre LM, Sangfelt O. FBXL12 degrades FANCD2 to regulate replication recovery and promote cancer cell survival under conditions of replication stress. Mol Cell 2023; 83:3720-3739.e8. [PMID: 37591242 PMCID: PMC10592106 DOI: 10.1016/j.molcel.2023.07.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 05/14/2023] [Accepted: 07/26/2023] [Indexed: 08/19/2023]
Abstract
Fanconi anemia (FA) signaling, a key genomic maintenance pathway, is activated in response to replication stress. Here, we report that phosphorylation of the pivotal pathway protein FANCD2 by CHK1 triggers its FBXL12-dependent proteasomal degradation, facilitating FANCD2 clearance at stalled replication forks. This promotes efficient DNA replication under conditions of CYCLIN E- and drug-induced replication stress. Reconstituting FANCD2-deficient fibroblasts with phosphodegron mutants failed to re-establish fork progression. In the absence of FBXL12, FANCD2 becomes trapped on chromatin, leading to replication stress and excessive DNA damage. In human cancers, FBXL12, CYCLIN E, and FA signaling are positively correlated, and FBXL12 upregulation is linked to reduced survival in patients with high CYCLIN E-expressing breast tumors. Finally, depletion of FBXL12 exacerbated oncogene-induced replication stress and sensitized cancer cells to drug-induced replication stress by WEE1 inhibition. Collectively, our results indicate that FBXL12 constitutes a vulnerability and a potential therapeutic target in CYCLIN E-overexpressing cancers.
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Affiliation(s)
- Andrä Brunner
- Department of Cell and Molecular Biology, Karolinska Institutet, Solna 17165, Stockholms län, Sweden.
| | - Qiuzhen Li
- Department of Cell and Molecular Biology, Karolinska Institutet, Solna 17165, Stockholms län, Sweden
| | - Samuele Fisicaro
- Department of Cell and Molecular Biology, Karolinska Institutet, Solna 17165, Stockholms län, Sweden
| | - Alexandros Kourtesakis
- Department of Cell and Molecular Biology, Karolinska Institutet, Solna 17165, Stockholms län, Sweden
| | - Johanna Viiliäinen
- Department of Cell and Molecular Biology, Karolinska Institutet, Solna 17165, Stockholms län, Sweden
| | - Henrik J Johansson
- Department of Oncology and Pathology, Karolinska Institutet, Science for Life Laboratory, Solna 17165, Stockholms län, Sweden
| | - Vijaya Pandey
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles 90095, CA, USA
| | - Adarsh K Mayank
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles 90095, CA, USA
| | - Janne Lehtiö
- Department of Oncology and Pathology, Karolinska Institutet, Science for Life Laboratory, Solna 17165, Stockholms län, Sweden
| | - James A Wohlschlegel
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles 90095, CA, USA
| | - Charles Spruck
- NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla 92037, CA, USA
| | - Juha K Rantala
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, South Yorkshire, UK; Misvik Biology, Turku 20520, Finland
| | - Lukas M Orre
- Department of Oncology and Pathology, Karolinska Institutet, Science for Life Laboratory, Solna 17165, Stockholms län, Sweden
| | - Olle Sangfelt
- Department of Cell and Molecular Biology, Karolinska Institutet, Solna 17165, Stockholms län, Sweden.
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