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McMahon A, Zhao J, Yan S. Ubiquitin-mediated regulation of APE2 protein abundance. J Biol Chem 2024; 300:107337. [PMID: 38705397 PMCID: PMC11157268 DOI: 10.1016/j.jbc.2024.107337] [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: 10/30/2023] [Revised: 04/12/2024] [Accepted: 04/24/2024] [Indexed: 05/07/2024] Open
Abstract
APE2 plays important roles in the maintenance of genomic and epigenomic stability including DNA repair and DNA damage response. Accumulating evidence has suggested that APE2 is upregulated in multiple cancers at the protein and mRNA levels and that APE2 upregulation is correlative with higher and lower overall survival of cancer patients depending on tumor type. However, it remains unknown how APE2 protein abundance is maintained and regulated in cells. Here, we provide the first evidence of APE2 regulation via the posttranslational modification ubiquitin. APE2 is poly-ubiquitinated via K48-linked chains and degraded via the ubiquitin-proteasome system where K371 is the key residue within APE2 responsible for its ubiquitination and degradation. We further characterize MKRN3 as the E3 ubiquitin ligase for APE2 ubiquitination in cells and in vitro. In summary, this study offers the first definition of the APE2 proteostasis network and lays the foundation for future studies pertaining to the posttranslational modification regulation and functions of APE2 in genome integrity and cancer etiology/treatment.
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Affiliation(s)
- Anne McMahon
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, North Carolina, USA
| | - Jianjun Zhao
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Shan Yan
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, North Carolina, USA; School of Data Science, University of North Carolina at Charlotte, Charlotte, North Carolina, USA; Center for Biomedical Engineering and Science, University of North Carolina at Charlotte, Charlotte, North Carolina, USA.
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Sampathkumar A, Zhong C, Tang Y, Fujita Y, Ito M, Shinohara A. Replication protein-A, RPA, plays a pivotal role in the maintenance of recombination checkpoint in yeast meiosis. Sci Rep 2024; 14:9550. [PMID: 38664461 PMCID: PMC11045724 DOI: 10.1038/s41598-024-60082-x] [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: 09/27/2023] [Accepted: 04/18/2024] [Indexed: 04/28/2024] Open
Abstract
DNA double-strand breaks (DSBs) activate DNA damage responses (DDRs) in both mitotic and meiotic cells. A single-stranded DNA (ssDNA) binding protein, Replication protein-A (RPA) binds to the ssDNA formed at DSBs to activate ATR/Mec1 kinase for the response. Meiotic DSBs induce homologous recombination monitored by a meiotic DDR called the recombination checkpoint that blocks the pachytene exit in meiotic prophase I. In this study, we further characterized the essential role of RPA in the maintenance of the recombination checkpoint during Saccharomyces cerevisiae meiosis. The depletion of an RPA subunit, Rfa1, in a recombination-defective dmc1 mutant, fully alleviates the pachytene arrest with the persistent unrepaired DSBs. RPA depletion decreases the activity of a meiosis-specific CHK2 homolog, Mek1 kinase, which in turn activates the Ndt80 transcriptional regulator for pachytene exit. These support the idea that RPA is a sensor of ssDNAs for the activation of meiotic DDR. Rfa1 depletion also accelerates the prophase I delay in the zip1 mutant defective in both chromosome synapsis and the recombination, consistent with the notion that the accumulation of ssDNAs rather than defective synapsis triggers prophase I delay in the zip1 mutant.
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Affiliation(s)
- Arivarasan Sampathkumar
- Institute for Protein Research, University of Osaka, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Chen Zhong
- Institute for Protein Research, University of Osaka, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yuting Tang
- Institute for Protein Research, University of Osaka, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yurika Fujita
- Institute for Protein Research, University of Osaka, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Masaru Ito
- Institute for Protein Research, University of Osaka, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Akira Shinohara
- Institute for Protein Research, University of Osaka, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
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Hussen AS, Kravitz HL, Freudenthal BD, Whitaker AM. Oxidative DNA damage on the VEGF G-quadruplex forming promoter is repaired via long-patch BER. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024; 65 Suppl 1:25-39. [PMID: 37606505 PMCID: PMC10984112 DOI: 10.1002/em.22570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/01/2023] [Accepted: 08/20/2023] [Indexed: 08/23/2023]
Abstract
In response to oxidative damage, base excision repair (BER) enzymes perturb the structural equilibrium of the VEGF promoter between B-form and G4 DNA conformations, resulting in epigenetic-like modifications of gene expression. However, the mechanistic details remain enigmatic, including the activity and coordination of BER enzymes on the damaged G4 promoter. To address this, we investigated the ability of each BER factor to conduct its repair activity on VEGF promoter G4 DNA substrates by employing pre-steady-state kinetics assays and in vitro coupled BER assays. OGG1 was able to initiate BER on double-stranded VEGF promoter G4 DNA substrates. Moreover, pre-steady-state kinetics revealed that compared to B-form DNA, APE1 repair activity on the G4 was decreased ~two-fold and is the result of slower product release as opposed to inefficient strand cleavage. Interestingly, Pol β performs multiple insertions on G4 substrates via strand displacement DNA synthesis in contrast to a single insertion on B-form DNA. The multiple insertions inhibit ligation of the Pol β products, and hence BER is not completed on the VEGF G4 promoter substrates through canonical short-patch BER. Instead, repair requires the long-patch BER flap-endonuclease activity of FEN1 in response to the multiple insertions by Pol β prior to ligation. Because the BER proteins and their repair activities are a key part of the VEGF transcriptional enhancement in response to oxidative DNA damage of the G4 VEGF promoter, the new insights reported here on BER activity in the context of this promoter are relevant toward understanding the mechanism of transcriptional regulation.
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Affiliation(s)
- Adil S. Hussen
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Haley L. Kravitz
- Nuclear Dynamics and Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA
| | - Bret D. Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Amy M. Whitaker
- Nuclear Dynamics and Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA
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Hoitsma NM, Norris J, Khoang TH, Kaushik V, Chadda R, Antony E, Hedglin M, Freudenthal BD. Mechanistic insight into AP-endonuclease 1 cleavage of abasic sites at stalled replication fork mimics. Nucleic Acids Res 2023; 51:6738-6753. [PMID: 37264933 PMCID: PMC10359615 DOI: 10.1093/nar/gkad481] [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: 11/07/2022] [Revised: 05/13/2023] [Accepted: 05/31/2023] [Indexed: 06/03/2023] Open
Abstract
Many types of damage, including abasic sites, block replicative DNA polymerases causing replication fork uncoupling and generating ssDNA. AP-Endonuclease 1 (APE1) has been shown to cleave abasic sites in ssDNA. Importantly, APE1 cleavage of ssDNA at a replication fork has significant biological implications by generating double strand breaks that could collapse the replication fork. Despite this, the molecular basis and efficiency of APE1 processing abasic sites at replication forks remain elusive. Here, we investigate APE1 cleavage of abasic substrates that mimic APE1 interactions at stalled replication forks or gaps. We determine that APE1 has robust activity on these substrates, like dsDNA, and report rates for cleavage and product release. X-ray structures visualize the APE1 active site, highlighting an analogous mechanism is used to process ssDNA substrates as canonical APE1 activity on dsDNA. However, mutational analysis reveals R177 to be uniquely critical for the APE1 ssDNA cleavage mechanism. Additionally, we investigate the interplay between APE1 and Replication Protein A (RPA), the major ssDNA-binding protein at replication forks, revealing that APE1 can cleave an abasic site while RPA is still bound to the DNA. Together, this work provides molecular level insights into abasic ssDNA processing by APE1, including the presence of RPA.
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Affiliation(s)
- Nicole M Hoitsma
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Jessica Norris
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Thu H Khoang
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Vikas Kaushik
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Rahul Chadda
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Edwin Antony
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
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Malfatti MC, Bellina A, Antoniali G, Tell G. Revisiting Two Decades of Research Focused on Targeting APE1 for Cancer Therapy: The Pros and Cons. Cells 2023; 12:1895. [PMID: 37508559 PMCID: PMC10378182 DOI: 10.3390/cells12141895] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 07/06/2023] [Accepted: 07/14/2023] [Indexed: 07/30/2023] Open
Abstract
APE1 is an essential endodeoxyribonuclease of the base excision repair pathway that maintains genome stability. It was identified as a pivotal factor favoring tumor progression and chemoresistance through the control of gene expression by a redox-based mechanism. APE1 is overexpressed and serum-secreted in different cancers, representing a prognostic and predictive factor and a promising non-invasive biomarker. Strategies directly targeting APE1 functions led to the identification of inhibitors showing potential therapeutic value, some of which are currently in clinical trials. Interestingly, evidence indicates novel roles of APE1 in RNA metabolism that are still not fully understood, including its activity in processing damaged RNA in chemoresistant phenotypes, regulating onco-miRNA maturation, and oxidized RNA decay. Recent data point out a control role for APE1 in the expression and sorting of onco-miRNAs within secreted extracellular vesicles. This review is focused on giving a portrait of the pros and cons of the last two decades of research aiming at the identification of inhibitors of the redox or DNA-repair functions of APE1 for the definition of novel targeted therapies for cancer. We will discuss the new perspectives in cancer therapy emerging from the unexpected finding of the APE1 role in miRNA processing for personalized therapy.
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Affiliation(s)
- Matilde Clarissa Malfatti
- Laboratory of Molecular Biology and DNA Repair, Department of Medicine, University of Udine, 33100 Udine, Italy
| | - Alessia Bellina
- Laboratory of Molecular Biology and DNA Repair, Department of Medicine, University of Udine, 33100 Udine, Italy
| | - Giulia Antoniali
- Laboratory of Molecular Biology and DNA Repair, Department of Medicine, University of Udine, 33100 Udine, Italy
| | - Gianluca Tell
- Laboratory of Molecular Biology and DNA Repair, Department of Medicine, University of Udine, 33100 Udine, Italy
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Driscoll G, Yan S. Maintaining chromosome and genome stability by the RPA-RNF20-SNF2H cascade. Proc Natl Acad Sci U S A 2023; 120:e2306455120. [PMID: 37276422 PMCID: PMC10268305 DOI: 10.1073/pnas.2306455120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023] Open
Affiliation(s)
- Garrett Driscoll
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC28223
| | - Shan Yan
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC28223
- School of Data Science, University of North Carolina at Charlotte, Charlotte, NC28223
- Center for Biomedical Engineering and Science, University of North Carolina at Charlotte, Charlotte, NC28223
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