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Boukoura S, Larsen DH. Nucleolar organization and ribosomal DNA stability in response to DNA damage. Curr Opin Cell Biol 2024; 89:102380. [PMID: 38861757 DOI: 10.1016/j.ceb.2024.102380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 05/17/2024] [Accepted: 05/20/2024] [Indexed: 06/13/2024]
Abstract
Eukaryotic nuclei are structured into sub-compartments orchestrating various cellular functions. The nucleolus is the largest nuclear organelle: a biomolecular condensate with an architecture composed of immiscible fluids facilitating ribosome biogenesis. The nucleolus forms upon the transcription of the repetitive ribosomal RNA genes (rDNA) that cluster in this compartment. rDNA is intrinsically unstable and prone to rearrangements and copy number variation. Upon DNA damage, a specialized nucleolar-DNA Damage Response (n-DDR) is activated: nucleolar transcription is inhibited, the architecture is rearranged, and rDNA is relocated to the nucleolar periphery. Recent data have highlighted how the composition of nucleoli, its structure, chemical and physical properties, contribute to rDNA stability. In this mini-review we focus on recent data that start to reveal how nucleolar composition and the n-DDR work together to ensure rDNA integrity.
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Affiliation(s)
- Stavroula Boukoura
- Nucleolar Stress and Disease Group, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Dorthe Helena Larsen
- Nucleolar Stress and Disease Group, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark.
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2
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Trifault B, Mamontova V, Cossa G, Ganskih S, Wei Y, Hofstetter J, Bhandare P, Baluapuri A, Nieto B, Solvie D, Ade CP, Gallant P, Wolf E, Larsen DH, Munschauer M, Burger K. Nucleolar detention of NONO shields DNA double-strand breaks from aberrant transcripts. Nucleic Acids Res 2024; 52:3050-3068. [PMID: 38224452 PMCID: PMC11014278 DOI: 10.1093/nar/gkae022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 12/11/2023] [Accepted: 01/04/2024] [Indexed: 01/16/2024] Open
Abstract
RNA-binding proteins emerge as effectors of the DNA damage response (DDR). The multifunctional non-POU domain-containing octamer-binding protein NONO/p54nrb marks nuclear paraspeckles in unperturbed cells, but also undergoes re-localization to the nucleolus upon induction of DNA double-strand breaks (DSBs). However, NONO nucleolar re-localization is poorly understood. Here we show that the topoisomerase II inhibitor etoposide stimulates the production of RNA polymerase II-dependent, DNA damage-inducible antisense intergenic non-coding RNA (asincRNA) in human cancer cells. Such transcripts originate from distinct nucleolar intergenic spacer regions and form DNA-RNA hybrids to tether NONO to the nucleolus in an RNA recognition motif 1 domain-dependent manner. NONO occupancy at protein-coding gene promoters is reduced by etoposide, which attenuates pre-mRNA synthesis, enhances NONO binding to pre-mRNA transcripts and is accompanied by nucleolar detention of a subset of such transcripts. The depletion or mutation of NONO interferes with detention and prolongs DSB signalling. Together, we describe a nucleolar DDR pathway that shields NONO and aberrant transcripts from DSBs to promote DNA repair.
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Affiliation(s)
- Barbara Trifault
- Mildred Scheel Early Career Center for Cancer Research (Mildred-Scheel-Nachwuchszentrum, MSNZ) Würzburg, University Hospital Würzburg, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
- Department of Biochemistry and Molecular Biology, Biocenter of the University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Victoria Mamontova
- Mildred Scheel Early Career Center for Cancer Research (Mildred-Scheel-Nachwuchszentrum, MSNZ) Würzburg, University Hospital Würzburg, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
- Department of Biochemistry and Molecular Biology, Biocenter of the University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Giacomo Cossa
- Department of Biochemistry and Molecular Biology, Biocenter of the University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Sabina Ganskih
- Helmholtz Institute for RNA-based Infection Research, Helmholtz-Center for Infection Research, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
| | - Yuanjie Wei
- Helmholtz Institute for RNA-based Infection Research, Helmholtz-Center for Infection Research, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
| | - Julia Hofstetter
- Cancer Systems Biology Group, Theodor Boveri Institute, Biocenter, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Pranjali Bhandare
- Cancer Systems Biology Group, Theodor Boveri Institute, Biocenter, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Apoorva Baluapuri
- Cancer Systems Biology Group, Theodor Boveri Institute, Biocenter, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Blanca Nieto
- Nucleolar Stress and Disease Group, Danish Cancer Institute, Strandboulevarden 49, Copenhagen, Denmark
| | - Daniel Solvie
- Department of Biochemistry and Molecular Biology, Biocenter of the University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Carsten P Ade
- Department of Biochemistry and Molecular Biology, Biocenter of the University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Peter Gallant
- Department of Biochemistry and Molecular Biology, Biocenter of the University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Elmar Wolf
- Cancer Systems Biology Group, Theodor Boveri Institute, Biocenter, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Dorthe H Larsen
- Nucleolar Stress and Disease Group, Danish Cancer Institute, Strandboulevarden 49, Copenhagen, Denmark
| | - Mathias Munschauer
- Helmholtz Institute for RNA-based Infection Research, Helmholtz-Center for Infection Research, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
| | - Kaspar Burger
- Mildred Scheel Early Career Center for Cancer Research (Mildred-Scheel-Nachwuchszentrum, MSNZ) Würzburg, University Hospital Würzburg, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
- Department of Biochemistry and Molecular Biology, Biocenter of the University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
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Chen L, Gai X, Yu X. Pre-rRNA facilitates the recruitment of RAD51AP1 to DNA double-strand breaks. J Biol Chem 2024; 300:107115. [PMID: 38403248 PMCID: PMC10959706 DOI: 10.1016/j.jbc.2024.107115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 02/02/2024] [Accepted: 02/13/2024] [Indexed: 02/27/2024] Open
Abstract
RAD51-associated protein 1 (RAD51AP1) is known to promote homologous recombination (HR) repair. However, the precise mechanism of RAD51AP1 in HR repair is unclear. Here, we identify that RAD51AP1 associates with pre-rRNA. Both the N terminus and C terminus of RAD51AP1 recognize pre-rRNA. Pre-rRNA not only colocalizes with RAD51AP1 at double-strand breaks (DSBs) but also facilitates the recruitment of RAD51AP1 to DSBs. Consistently, transient inhibition of pre-rRNA synthesis by RNA polymerase I inhibitor suppresses the recruitment of RAD51AP1 as well as HR repair. Moreover, RAD51AP1 forms liquid-liquid phase separation in the presence of pre-rRNA in vitro, which may be the molecular mechanism of RAD51AP1 foci formation. Taken together, our results demonstrate that pre-rRNA mediates the relocation of RAD51AP1 to DSBs for HR repair.
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Affiliation(s)
- Linlin Chen
- School of Life Sciences, Fudan University, Shanghai, China; School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
| | - Xiaochen Gai
- School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang Province, China
| | - Xiaochun Yu
- School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang Province, China.
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Böğürcü-Seidel N, Ritschel N, Acker T, Németh A. Beyond ribosome biogenesis: noncoding nucleolar RNAs in physiology and tumor biology. Nucleus 2023; 14:2274655. [PMID: 37906621 PMCID: PMC10730139 DOI: 10.1080/19491034.2023.2274655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 10/19/2023] [Indexed: 11/02/2023] Open
Abstract
The nucleolus, the largest subcompartment of the nucleus, stands out from the nucleoplasm due to its exceptionally high local RNA and low DNA concentrations. Within this central hub of nuclear RNA metabolism, ribosome biogenesis is the most prominent ribonucleoprotein (RNP) biogenesis process, critically determining the structure and function of the nucleolus. However, recent studies have shed light on other roles of the nucleolus, exploring the interplay with various noncoding RNAs that are not directly involved in ribosome synthesis. This review focuses on this intriguing topic and summarizes the techniques to study and the latest findings on nucleolar long noncoding RNAs (lncRNAs) as well as microRNAs (miRNAs) in the context of nucleolus biology beyond ribosome biogenesis. We particularly focus on the multifaceted roles of the nucleolus and noncoding RNAs in physiology and tumor biology.
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Affiliation(s)
| | - Nadja Ritschel
- Institute of Neuropathology, Justus Liebig University Giessen, Giessen, Germany
| | - Till Acker
- Institute of Neuropathology, Justus Liebig University Giessen, Giessen, Germany
| | - Attila Németh
- Institute of Neuropathology, Justus Liebig University Giessen, Giessen, Germany
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Li C, Li Z, Wu Z, Lu H. Phase separation in gene transcription control. Acta Biochim Biophys Sin (Shanghai) 2023; 55:1052-1063. [PMID: 37265348 PMCID: PMC10415188 DOI: 10.3724/abbs.2023099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 04/28/2023] [Indexed: 06/03/2023] Open
Abstract
Phase separation provides a general mechanism for the formation of biomolecular condensates, and it plays a vital role in regulating diverse cellular processes, including gene expression. Although the role of transcription factors and coactivators in regulating transcription has long been understood, how phase separation is involved in this process is just beginning to be explored. In this review, we highlight recent advance in elucidating the molecular mechanisms and functions of transcriptional condensates in gene expression control. We discuss the different condensates formed at each stage of the transcription cycle and how they are dynamically regulated in response to diverse cellular and extracellular cues that cause rapid changes in gene expression. Furthermore, we present new findings regarding the dysregulation of transcription condensates and their implications in human diseases.
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Affiliation(s)
- Chengyu Li
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell BiologyLife Sciences InstituteZhejiang UniversityHangzhou310058China
| | - Zhuo Li
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell BiologyLife Sciences InstituteZhejiang UniversityHangzhou310058China
| | - Zhibing Wu
- Department of OncologyAffiliated Zhejiang HospitalZhejiang University School of MedicineHangzhou310058China
| | - Huasong Lu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell BiologyLife Sciences InstituteZhejiang UniversityHangzhou310058China
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Feng S, Desotell A, Ross A, Jovanovic M, Manley JL. A nucleolar long "non-coding" RNA encodes a novel protein that functions in response to stress. Proc Natl Acad Sci U S A 2023; 120:e2221109120. [PMID: 36812203 PMCID: PMC9992852 DOI: 10.1073/pnas.2221109120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 01/14/2023] [Indexed: 02/24/2023] Open
Abstract
Certain long non-coding RNAs (lncRNAs) are known to contain small open reading frames that can be translated. Here we describe a much larger 25 kDa human protein, "Ribosomal IGS Encoded Protein" (RIEP), that remarkably is encoded by the well-characterized RNA polymerase (RNAP) II-transcribed nucleolar "promoter and pre-rRNA antisense" lncRNA (PAPAS). Strikingly, RIEP, which is conserved throughout primates but not found in other species, predominantly localizes to the nucleolus as well as mitochondria, but both exogenously expressed and endogenous RIEP increase in the nuclear and perinuclear regions upon heat shock (HS). RIEP associates specifically with the rDNA locus, increases levels of the RNA:DNA helicase Senataxin, and functions to sharply reduce DNA damage induced by heat shock. Proteomics analysis identified two mitochondrial proteins, C1QBP and CHCHD2, both known to have mitochondrial and nuclear functions, that we show interact directly, and relocalize following heat shock, with RIEP. Finally, it is especially notable that the rDNA sequences encoding RIEP are multifunctional, giving rise to an RNA that functions both as RIEP messenger RNA (mRNA) and as PAPAS lncRNA, as well as containing the promoter sequences responsible for rRNA synthesis by RNAP I. Our work has thus not only shown that a nucleolar "non-coding" RNA in fact encodes a protein, but also established a novel link between mitochondria and nucleoli that contributes to the cellular stress response.
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Affiliation(s)
- Shuang Feng
- Department of Biological Sciences, Columbia University, New York, NY10027
| | - Anthony Desotell
- Department of Biological Sciences, Columbia University, New York, NY10027
| | - Alison Ross
- Department of Biological Sciences, Columbia University, New York, NY10027
| | - Marko Jovanovic
- Department of Biological Sciences, Columbia University, New York, NY10027
| | - James L. Manley
- Department of Biological Sciences, Columbia University, New York, NY10027
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Regulation of RNA Polymerase I Stability and Function. Cancers (Basel) 2022; 14:cancers14235776. [PMID: 36497261 PMCID: PMC9737084 DOI: 10.3390/cancers14235776] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/21/2022] [Accepted: 11/21/2022] [Indexed: 11/27/2022] Open
Abstract
RNA polymerase I is a highly processive enzyme with fast initiation and elongation rates. The structure of Pol I, with its in-built RNA cleavage ability and incorporation of subunits homologous to transcription factors, enables it to quickly and efficiently synthesize the enormous amount of rRNA required for ribosome biogenesis. Each step of Pol I transcription is carefully controlled. However, cancers have highjacked these control points to switch the enzyme, and its transcription, on permanently. While this provides an exceptional benefit to cancer cells, it also creates a potential cancer therapeutic vulnerability. We review the current research on the regulation of Pol I transcription, and we discuss chemical biology efforts to develop new targeted agents against this process. Lastly, we highlight challenges that have arisen from the introduction of agents with promiscuous mechanisms of action and provide examples of agents with specificity and selectivity against Pol I.
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