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Prabhakar AT, James CD, Fontan CT, Otoa R, Wang X, Bristol ML, Yeager C, Hill RD, Dubey A, Wu SY, Chiang CM, Morgan IM. Direct interaction with the BRD4 carboxyl-terminal motif (CTM) and TopBP1 is required for human papillomavirus 16 E2 association with mitotic chromatin and plasmid segregation function. J Virol 2023; 97:e0078223. [PMID: 37712702 PMCID: PMC10617519 DOI: 10.1128/jvi.00782-23] [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: 05/24/2023] [Accepted: 07/25/2023] [Indexed: 09/16/2023] Open
Abstract
IMPORTANCE Human papillomavirus 16 (HPV16) is a causative agent in around 3%-4% of all human cancers, and currently, there are no anti-viral therapeutics available for combating this disease burden. In order to identify new therapeutic targets, we must increase our understanding of the HPV16 life cycle. Previously, we demonstrated that an interaction between E2 and the cellular protein TopBP1 mediates the plasmid segregation function of E2, allowing distribution of viral genomes into daughter nuclei following cell division. Here, we demonstrate that E2 interaction with an additional host protein, BRD4, is also essential for E2 segregation function, and that BRD4 exists in a complex with TopBP1. Overall, these results enhance our understanding of a critical part of the HPV16 life cycle and presents several therapeutic targets for disruption of the viral life cycle.
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Affiliation(s)
- Apurva T. Prabhakar
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Claire D. James
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Christian T. Fontan
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Raymonde Otoa
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Xu Wang
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Molly L. Bristol
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
- VCU Massey Cancer Center, Richmond, Virginia, USA
| | - Calvin Yeager
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Ronald D. Hill
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Aanchal Dubey
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
| | - Shwu-Yuan Wu
- Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Cheng-Ming Chiang
- Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Iain M. Morgan
- Virginia Commonwealth University (VCU), Philips Institute for Oral Health Research, School of Dentistry, Richmond, Virginia, USA
- VCU Massey Cancer Center, Richmond, Virginia, USA
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Prabhakar AT, James CD, Fontan CT, Otoa R, Wang X, Bristol ML, Hill RD, Dubey A, Wu SY, Chiang CM, Morgan IM. Direct interaction with the BRD4 carboxyl-terminal motif (CTM) and TopBP1 is required for human papillomavirus 16 E2 association with mitotic chromatin and plasmid segregation function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.25.542291. [PMID: 37292798 PMCID: PMC10245903 DOI: 10.1101/2023.05.25.542291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
During the human papillomavirus 16 life cycle, the E2 protein binds simultaneously to the viral genome and host chromatin throughout mitosis, ensuring viral genomes reside in daughter cell nuclei following cell division. Previously, we demonstrated that CK2 phosphorylation of E2 on serine 23 promotes interaction with TopBP1, and that this interaction is required for optimum E2 mitotic chromatin association and plasmid segregation function. Others have implicated BRD4 in mediating the plasmid segregation function of E2 and we have demonstrated that there is a TopBP1-BRD4 complex in the cell. We therefore further investigated the role of the E2-BRD4 interaction in mediating E2 association with mitotic chromatin and plasmid segregation function. Using a combination of immunofluorescence and our novel plasmid segregation assay in U2OS and N/Tert-1 cells stably expressing a variety of E2 mutants, we report that direct interaction with the BRD4 carboxyl-terminal motif (CTM) and TopBP1 is required for E2 association with mitotic chromatin and plasmid segregation. We also identify a novel TopBP1 mediated interaction between E2 and the BRD4 extra-terminal (ET) domain in vivo . Overall, the results demonstrate that direct interaction with TopBP1 and the BRD4 CTM are required for E2 mitotic chromatin association and plasmid segregation function. Disruption of this complex offers therapeutic options for targeting segregation of viral genomes into daughter cells, potentially combatting HPV16 infections, and cancers that retain episomal genomes. Importance HPV16 is a causative agent in around 3-4% of all human cancers and currently there are no anti-viral therapeutics available for combating this disease burden. In order to identify new therapeutic targets, we must increase our understanding of the HPV16 life cycle. Previously, we demonstrated that an interaction between E2 and the cellular protein TopBP1 mediates the plasmid segregation function of E2, allowing distribution of viral genomes into daughter nuclei following cell division. Here, we demonstrate that E2 interaction with an additional host protein, BRD4, is also essential for E2 segregation function, and that BRD4 exists in a complex with TopBP1. Overall, these results enhance our understanding of a critical part of the HPV16 life cycle and presents several therapeutic targets for disruption of the viral life cycle.
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Interaction with TopBP1 Is Required for Human Papillomavirus 16 E2 Plasmid Segregation/Retention Function during Mitosis. J Virol 2022; 96:e0083022. [PMID: 35880889 PMCID: PMC9400484 DOI: 10.1128/jvi.00830-22] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomavirus 16 (HPV16) E2 is a DNA-binding protein that regulates transcription, replication and potentially, segregation of the HPV16 genome during the viral life cycle. In the segregation model, E2 simultaneously binds to viral and host chromatin, acting as a bridge to ensure that viral genomes reside in daughter nuclei following cell division. The host chromatin receptor for E2 mediating this function is unknown. Recently, we demonstrated that CK2 phosphorylation of E2 on serine 23 (S23) is required for interaction with TopBP1, and that this interaction promotes E2 and TopBP1 recruitment to mitotic chromatin. Here, we demonstrate that in U2OS cells expressing wild-type E2 and a non-TopBP1-binding mutant (S23A, serine 23 mutated to alanine), interaction with TopBP1 is essential for E2 recruitment of plasmids to mitotic chromatin. Using novel quantitative segregation assays, we demonstrate that interaction with TopBP1 is required for E2 plasmid segregation function in U2OS and N/Tert-1 cells. Small interfering RNA (siRNA) knockdown of TopBP1 or CK2 enzyme components disrupts E2 segregation/retention function. The interaction of E2 with TopBP1 promotes increased levels of E2 protein during mitosis in U2OS and N/Tert-1 cells, as well as in human foreskin keratinocytes (HFK) immortalized by the HPV16 genome. Overall, our results demonstrate that E2 has plasmid segregation activity, and that the E2-TopBP1 interaction is essential for this E2 function. IMPORTANCE HPV16 causes 3% to 4% of all human cancers. It is proposed that during the viral life cycle, the viral genome is actively segregated into daughter nuclei, ensuring viral replication in the subsequent S phase. The E2 protein potentially bridges the viral and host genomes during mitosis to mediate segregation of the circular viral plasmid. Here, we demonstrate that E2 has the ability to mediate plasmid segregation, and that this function is dependent upon interaction with the host protein TopBP1. Additionally, we demonstrate that the E2-TopBP1 interaction promotes enhanced E2 expression during mitosis, which likely promotes the plasmid segregation function of E2. Overall, our results present a mechanism of how HPV16 can segregate its viral genome during an active infection, a critical aspect of the viral life cycle.
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Day M, Oliver AW, Pearl LH. Phosphorylation-dependent assembly of DNA damage response systems and the central roles of TOPBP1. DNA Repair (Amst) 2021; 108:103232. [PMID: 34678589 PMCID: PMC8651625 DOI: 10.1016/j.dnarep.2021.103232] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 11/11/2022]
Abstract
The cellular response to DNA damage (DDR) that causes replication collapse and/or DNA double strand breaks, is characterised by a massive change in the post-translational modifications (PTM) of hundreds of proteins involved in the detection and repair of DNA damage, and the communication of the state of damage to the cellular systems that regulate replication and cell division. A substantial proportion of these PTMs involve targeted phosphorylation, which among other effects, promotes the formation of multiprotein complexes through the specific binding of phosphorylated motifs on one protein, by specialised domains on other proteins. Understanding the nature of these phosphorylation mediated interactions allows definition of the pathways and networks that coordinate the DDR, and helps identify new targets for therapeutic intervention that may be of benefit in the treatment of cancer, where DDR plays a key role. In this review we summarise the present understanding of how phosphorylated motifs are recognised by BRCT domains, which occur in many DDR proteins. We particularly focus on TOPBP1 - a multi-BRCT domain scaffold protein with essential roles in replication and the repair and signalling of DNA damage.
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Affiliation(s)
- Matthew Day
- Cancer Research UK DNA Repair Enzymes Group, Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Antony W Oliver
- Cancer Research UK DNA Repair Enzymes Group, Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Laurence H Pearl
- Cancer Research UK DNA Repair Enzymes Group, Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK; Division of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW1E 6BT, UK.
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Bagge J, Oestergaard VH, Lisby M. Functions of TopBP1 in preserving genome integrity during mitosis. Semin Cell Dev Biol 2020; 113:57-64. [PMID: 32912640 DOI: 10.1016/j.semcdb.2020.08.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 07/06/2020] [Accepted: 08/26/2020] [Indexed: 12/20/2022]
Abstract
TopBP1/Rad4/Dpb11 is an essential eukaryotic protein with important roles in DNA replication, DNA repair, DNA damage checkpoint activation, and chromosome segregation. TopBP1 serves as a scaffold to assemble protein complexes in a phosphorylation-dependent manner via its multiple BRCT-repeats. Recently, it has become clear that TopBP1 is repurposed to scaffold different processes dependent on cell cycle regulated changes in phosphorylation of client proteins. Here we review the functions of human TopBP1 in maintaining genome integrity during mitosis.
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Affiliation(s)
- Jonas Bagge
- Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Vibe H Oestergaard
- Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Michael Lisby
- Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
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Leimbacher PA, Jones SE, Shorrocks AMK, de Marco Zompit M, Day M, Blaauwendraad J, Bundschuh D, Bonham S, Fischer R, Fink D, Kessler BM, Oliver AW, Pearl LH, Blackford AN, Stucki M. MDC1 Interacts with TOPBP1 to Maintain Chromosomal Stability during Mitosis. Mol Cell 2019; 74:571-583.e8. [PMID: 30898438 PMCID: PMC6509287 DOI: 10.1016/j.molcel.2019.02.014] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 12/30/2018] [Accepted: 02/11/2019] [Indexed: 12/29/2022]
Abstract
In mitosis, cells inactivate DNA double-strand break (DSB) repair pathways to preserve genome stability. However, some early signaling events still occur, such as recruitment of the scaffold protein MDC1 to phosphorylated histone H2AX at DSBs. Yet, it remains unclear whether these events are important for maintaining genome stability during mitosis. Here, we identify a highly conserved protein-interaction surface in MDC1 that is phosphorylated by CK2 and recognized by the DNA-damage response mediator protein TOPBP1. Disruption of MDC1-TOPBP1 binding causes a specific loss of TOPBP1 recruitment to DSBs in mitotic but not interphase cells, accompanied by mitotic radiosensitivity, increased micronuclei, and chromosomal instability. Mechanistically, we find that TOPBP1 forms filamentous structures capable of bridging MDC1 foci in mitosis, indicating that MDC1-TOPBP1 complexes tether DSBs until repair is reactivated in the following G1 phase. Thus, we reveal an important, hitherto-unnoticed cooperation between MDC1 and TOPBP1 in maintaining genome stability during cell division.
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Affiliation(s)
- Pia-Amata Leimbacher
- Department of Gynecology, University Hospital and University of Zurich, Wagistrasse 14, 8952 Schlieren, Switzerland
| | - Samuel E Jones
- Department of Oncology, Medical Research Council Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK; Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Ann-Marie K Shorrocks
- Department of Oncology, Medical Research Council Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK; Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Mara de Marco Zompit
- Department of Gynecology, University Hospital and University of Zurich, Wagistrasse 14, 8952 Schlieren, Switzerland
| | - Matthew Day
- Cancer Research UK DNA Repair Enzymes Group, Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer BN1 9RQ, UK
| | - Jordy Blaauwendraad
- Department of Gynecology, University Hospital and University of Zurich, Wagistrasse 14, 8952 Schlieren, Switzerland
| | - Diana Bundschuh
- Department of Gynecology, University Hospital and University of Zurich, Wagistrasse 14, 8952 Schlieren, Switzerland
| | - Sarah Bonham
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK
| | - Roman Fischer
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK
| | - Daniel Fink
- Department of Gynecology, University Hospital and University of Zurich, Wagistrasse 14, 8952 Schlieren, Switzerland
| | - Benedikt M Kessler
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK
| | - Antony W Oliver
- Cancer Research UK DNA Repair Enzymes Group, Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer BN1 9RQ, UK
| | - Laurence H Pearl
- Cancer Research UK DNA Repair Enzymes Group, Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer BN1 9RQ, UK
| | - Andrew N Blackford
- Department of Oncology, Medical Research Council Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK; Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford OX3 7DQ, UK.
| | - Manuel Stucki
- Department of Gynecology, University Hospital and University of Zurich, Wagistrasse 14, 8952 Schlieren, Switzerland.
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