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Espinoza JA, Kanellis DC, Saproo S, Leal K, Martinez J, Bartek J, Lindström M. Chromatin damage generated by DNA intercalators leads to degradation of RNA Polymerase II. Nucleic Acids Res 2024; 52:4151-4166. [PMID: 38340348 PMCID: PMC11077059 DOI: 10.1093/nar/gkae069] [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: 03/13/2023] [Revised: 01/16/2024] [Accepted: 01/23/2024] [Indexed: 02/12/2024] Open
Abstract
In cancer therapy, DNA intercalators are mainly known for their capacity to kill cells by inducing DNA damage. Recently, several DNA intercalators have attracted much interest given their ability to inhibit RNA Polymerase I transcription (BMH-21), evict histones (Aclarubicin) or induce chromatin trapping of FACT (Curaxin CBL0137). Interestingly, these DNA intercalators lack the capacity to induce DNA damage while still retaining cytotoxic effects and stabilize p53. Herein, we report that these DNA intercalators impact chromatin biology by interfering with the chromatin stability of RNA polymerases I, II and III. These three compounds have the capacity to induce degradation of RNA polymerase II and they simultaneously enable the trapping of Topoisomerases TOP2A and TOP2B on the chromatin. In addition, BMH-21 also acts as a catalytic inhibitor of Topoisomerase II, resembling Aclarubicin. Moreover, BMH-21 induces chromatin trapping of the histone chaperone FACT and propels accumulation of Z-DNA and histone eviction, similarly to Aclarubicin and CBL0137. These DNA intercalators have a cumulative impact on general transcription machinery by inducing accumulation of topological defects and impacting nuclear chromatin. Therefore, their cytotoxic capabilities may be the result of compounding deleterious effects on chromatin homeostasis.
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Affiliation(s)
- Jaime A Espinoza
- Science for Life Laboratory, Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
| | - Dimitris C Kanellis
- Science for Life Laboratory, Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
| | - Sheetanshu Saproo
- Science for Life Laboratory, Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
| | - Karla Leal
- Science for Life Laboratory, Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
| | - Johana Fernandez Martinez
- Science for Life Laboratory, Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
| | - Jiri Bartek
- Science for Life Laboratory, Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
- Danish Cancer Society Research Center, DK-2100 Copenhagen, Denmark
| | - Mikael S Lindström
- Science for Life Laboratory, Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 21 Stockholm, Sweden
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Harold C. All these screens that we've done: how functional genetic screens have informed our understanding of ribosome biogenesis. Biosci Rep 2023; 43:BSR20230631. [PMID: 37335083 PMCID: PMC10329186 DOI: 10.1042/bsr20230631] [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: 04/09/2023] [Revised: 06/08/2023] [Accepted: 06/19/2023] [Indexed: 06/21/2023] Open
Abstract
Ribosome biogenesis is the complex and essential process that ultimately leads to the synthesis of cellular proteins. Understanding each step of this essential process is imperative to increase our understanding of basic biology, but also more critically, to provide novel therapeutic avenues for genetic and developmental diseases such as ribosomopathies and cancers which can arise when this process is impaired. In recent years, significant advances in technology have made identifying and characterizing novel human regulators of ribosome biogenesis via high-content, high-throughput screens. Additionally, screening platforms have been used to discover novel therapeutics for cancer. These screens have uncovered a wealth of knowledge regarding novel proteins involved in human ribosome biogenesis, from the regulation of the transcription of the ribosomal RNA to global protein synthesis. Specifically, comparing the discovered proteins in these screens showed interesting connections between large ribosomal subunit (LSU) maturation factors and earlier steps in ribosome biogenesis, as well as overall nucleolar integrity. In this review, a discussion of the current standing of screens for human ribosome biogenesis factors through the lens of comparing the datasets and discussing the biological implications of the areas of overlap will be combined with a look toward other technologies and how they can be adapted to discover more factors involved in ribosome synthesis, and answer other outstanding questions in the field.
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Affiliation(s)
- Cecelia M. Harold
- Department of Genetics, Yale School of Medicine, New Haven, CT, U.S.A
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Ford BL, Wei T, Liu H, Scull CE, Najmi SM, Pitts S, Fan W, Schneider DA, Laiho M. Expression of RNA polymerase I catalytic core is influenced by RPA12. PLoS One 2023; 18:e0285660. [PMID: 37167337 PMCID: PMC10174586 DOI: 10.1371/journal.pone.0285660] [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: 12/30/2022] [Accepted: 04/27/2023] [Indexed: 05/13/2023] Open
Abstract
RNA Polymerase I (Pol I) has recently been recognized as a cancer therapeutic target. The activity of this enzyme is essential for ribosome biogenesis and is universally activated in cancers. The enzymatic activity of this multi-subunit complex resides in its catalytic core composed of RPA194, RPA135, and RPA12, a subunit with functions in RNA cleavage, transcription initiation and elongation. Here we explore whether RPA12 influences the regulation of RPA194 in human cancer cells. We use a specific small-molecule Pol I inhibitor BMH-21 that inhibits transcription initiation, elongation and ultimately activates the degradation of Pol I catalytic subunit RPA194. We show that silencing RPA12 causes alterations in the expression and localization of Pol I subunits RPA194 and RPA135. Furthermore, we find that despite these alterations not only does the Pol I core complex between RPA194 and RPA135 remain intact upon RPA12 knockdown, but the transcription of Pol I and its engagement with chromatin remain unaffected. The BMH-21-mediated degradation of RPA194 was independent of RPA12 suggesting that RPA12 affects the basal expression, but not the drug-inducible turnover of RPA194. These studies add to knowledge defining regulatory factors for the expression of this Pol I catalytic subunit.
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Affiliation(s)
- Brittany L. Ford
- Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
- Department of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Ting Wei
- Department of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Hester Liu
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America
| | - Catherine E. Scull
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Saman M. Najmi
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Stephanie Pitts
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America
| | - Wenjun Fan
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America
| | - David A. Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Marikki Laiho
- Department of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America
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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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