1
|
Glancy E, Choy N, Eckersley-Maslin MA. Bivalent chromatin: a developmental balancing act tipped in cancer. Biochem Soc Trans 2024; 52:217-229. [PMID: 38385532 PMCID: PMC10903468 DOI: 10.1042/bst20230426] [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: 11/21/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/23/2024]
Abstract
Bivalent chromatin is defined by the co-occurrence of otherwise opposing H3K4me3 and H3K27me3 modifications and is typically located at unmethylated promoters of lowly transcribed genes. In embryonic stem cells, bivalent chromatin has been proposed to poise developmental genes for future activation, silencing or stable repression upon lineage commitment. Normally, bivalent chromatin is kept in tight balance in cells, in part through the activity of the MLL/COMPASS-like and Polycomb repressive complexes that deposit the H3K4me3 and H3K27me3 modifications, respectively, but also emerging novel regulators including DPPA2/4, QSER1, BEND3, TET1 and METTL14. In cancers, both the deregulation of existing domains and the creation of de novo bivalent states is associated with either the activation or silencing of transcriptional programmes. This may facilitate diverse aspects of cancer pathology including epithelial-to-mesenchymal plasticity, chemoresistance and immune evasion. Here, we review current methods for detecting bivalent chromatin and discuss the factors involved in the formation and fine-tuning of bivalent domains. Finally, we examine how the deregulation of chromatin bivalency in the context of cancer could facilitate and/or reflect cancer cell adaptation. We propose a model in which bivalent chromatin represents a dynamic balance between otherwise opposing states, where the underlying DNA sequence is primed for the future activation or repression. Shifting this balance in any direction disrupts the tight equilibrium and tips cells into an altered epigenetic and phenotypic space, facilitating both developmental and cancer processes.
Collapse
Affiliation(s)
- Eleanor Glancy
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Natalie Choy
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Melanie A. Eckersley-Maslin
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria 3010, Australia
- Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| |
Collapse
|
2
|
Cong F, Long J, Liu J, Deng Z, Yan B, Liang C, Huang X, Liu J, Tang W. An integrative analysis revealing POLD2 as a tumor suppressive immune protein and prognostic biomarker in pan-cancer. Front Genet 2022; 13:877468. [PMID: 36081989 PMCID: PMC9447486 DOI: 10.3389/fgene.2022.877468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 07/22/2022] [Indexed: 11/15/2022] Open
Abstract
Introduction: POLD2 is an indispensable subunit of DNA polymerase δ, which is responsible for the synthesis of the backward accompanying strand in eukaryotic organisms. Current studies have found an association between POLD2 and the development of a variety of cancers. However, its value in cancer immunotherapy has not been fully established. Methods: POLD2 expression was analyzed using RNA expression and clinical data from TCGA and GTEx databases. The prognostic impact of POLD2 on tumor patients was analyzed using clinical survival data from TCGA. Gene enrichment analysis was performed using the R package “cluster analyzer” to explore the role of POLD2. We used the TIMER2 database to analyze the relationship between immune cell infiltration and POLD2 expression in TCGA. We downloaded relevant data from TCGA and analyzed the relationship between POLD2 and immune checkpoints, immunosuppressive genes, immune activating genes, chemokines and chemokine receptors. Results: POLD2 was significantly overexpressed in most tumors compared to normal tissue. High POLD2 expression was significantly associated with advanced tumor stage, significantly shorter overall survival and progression-free survival. Also, we found that POLD2 expression correlated strongly with immunomodulatory genes, and significantly negatively with most immune checkpoints (PD-L1, CTLA4, TIM3, and CD28). Pathway enrichment analysis suggests that low expression of POLD2 promotes immune regulation-related pathways and high expression promotes metabolic and DNA repair-related pathways. Furthermore, tumor microenvironment analysis suggests that high POLD2 expression inhibits infiltration of CD8+ T cells and CD4+ memory T cells. Discussion: In conclusion, POLD2 may be a molecular biomarker for pan-cancer prognosis and immunotherapy. It may serve as a potential target for new insights in human tumor prognosis prediction and immunotherapy assessment.
Collapse
Affiliation(s)
- Fengyun Cong
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
- Department of Gastroenteroanal Surgery, The First People’s Hospital of Nanning, Nanning, China
| | - Junxian Long
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
- Department of Gastroenteroanal Surgery, The First People’s Hospital of Nanning, Nanning, China
| | - Jun Liu
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Zhixiang Deng
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Binli Yan
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Cao Liang
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Xiaoliang Huang
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Jinxin Liu
- Department of Gastroenteroanal Surgery, The First People’s Hospital of Nanning, Nanning, China
- *Correspondence: Jinxin Liu, ; Weizhong Tang,
| | - Weizhong Tang
- Division of Colorectal and Anal Surgery, Department of Gastrointestinal Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
- *Correspondence: Jinxin Liu, ; Weizhong Tang,
| |
Collapse
|
3
|
The role of ATXR6 expression in modulating genome stability and transposable element repression in Arabidopsis. Proc Natl Acad Sci U S A 2022; 119:2115570119. [PMID: 35027454 PMCID: PMC8784105 DOI: 10.1073/pnas.2115570119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2021] [Indexed: 01/07/2023] Open
Abstract
The plant-specific H3K27me1 methyltransferases ATXR5 and ATXR6 play integral roles connecting epigenetic silencing with genomic stability. However, how H3K27me1 relates to these processes is poorly understood. In this study, we performed a comprehensive transcriptome analysis of tissue- and ploidy-specific expression in a hypomorphic atxr5/6 mutant and revealed that the tissue-specific defects correlate with residual ATXR6 expression. We also determined that ATXR5/6 function is essential for female germline development. Furthermore, we provide a comprehensive analysis of H3K27me1 changes in relation to other epigenetic marks. We also determined that some previously reported suppressors of atxr5/6 may act by restoring the levels of H3K27me1, such as through up-regulation of the ATXR6 transcript in the atxr6 hypomorphic promoter allele. ARABIDOPSIS TRITHORAX-RELATED PROTEIN 5 (ATXR5) AND ATXR6 are required for the deposition of H3K27me1 and for maintaining genomic stability in Arabidopsis. Reduction of ATXR5/6 activity results in activation of DNA damage response genes, along with tissue-specific derepression of transposable elements (TEs), chromocenter decompaction, and genomic instability characterized by accumulation of excess DNA from heterochromatin. How loss of ATXR5/6 and H3K27me1 leads to these phenotypes remains unclear. Here we provide extensive characterization of the atxr5/6 hypomorphic mutant by comprehensively examining gene expression and epigenetic changes in the mutant. We found that the tissue-specific phenotypes of TE derepression and excessive DNA in this atxr5/6 mutant correlated with residual ATXR6 expression from the hypomorphic ATXR6 allele. However, up-regulation of DNA damage genes occurred regardless of ATXR6 levels and thus appears to be a separable process. We also isolated an atxr6-null allele which showed that ATXR5 and ATXR6 are required for female germline development. Finally, we characterize three previously reported suppressors of the hypomorphic atxr5/6 mutant and show that these rescue atxr5/6 via distinct mechanisms, two of which involve increasing H3K27me1 levels.
Collapse
|
4
|
Eekhout T, Pedroza-Garcia JA, Kalhorzadeh P, De Jaeger G, De Veylder L. A Mutation in DNA Polymerase α Rescues WEE1KO Sensitivity to HU. Int J Mol Sci 2021; 22:9409. [PMID: 34502313 PMCID: PMC8430855 DOI: 10.3390/ijms22179409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/25/2021] [Accepted: 08/26/2021] [Indexed: 11/16/2022] Open
Abstract
During DNA replication, the WEE1 kinase is responsible for safeguarding genomic integrity by phosphorylating and thus inhibiting cyclin-dependent kinases (CDKs), which are the driving force of the cell cycle. Consequentially, wee1 mutant plants fail to respond properly to problems arising during DNA replication and are hypersensitive to replication stress. Here, we report the identification of the polα-2 mutant, mutated in the catalytic subunit of DNA polymerase α, as a suppressor mutant of wee1. The mutated protein appears to be less stable, causing a loss of interaction with its subunits and resulting in a prolonged S-phase.
Collapse
Affiliation(s)
- Thomas Eekhout
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; (T.E.); (J.A.P.-G.); (P.K.); (G.D.J.)
- Center for Plant Systems Biology, VIB, 9052 Gent, Belgium
| | - José Antonio Pedroza-Garcia
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; (T.E.); (J.A.P.-G.); (P.K.); (G.D.J.)
- Center for Plant Systems Biology, VIB, 9052 Gent, Belgium
| | - Pooneh Kalhorzadeh
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; (T.E.); (J.A.P.-G.); (P.K.); (G.D.J.)
- Center for Plant Systems Biology, VIB, 9052 Gent, Belgium
| | - Geert De Jaeger
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; (T.E.); (J.A.P.-G.); (P.K.); (G.D.J.)
- Center for Plant Systems Biology, VIB, 9052 Gent, Belgium
| | - Lieven De Veylder
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; (T.E.); (J.A.P.-G.); (P.K.); (G.D.J.)
- Center for Plant Systems Biology, VIB, 9052 Gent, Belgium
| |
Collapse
|
5
|
Bourguet P, López-González L, Gómez-Zambrano Á, Pélissier T, Hesketh A, Potok ME, Pouch-Pélissier MN, Perez M, Da Ines O, Latrasse D, White CI, Jacobsen SE, Benhamed M, Mathieu O. DNA polymerase epsilon is required for heterochromatin maintenance in Arabidopsis. Genome Biol 2020; 21:283. [PMID: 33234150 PMCID: PMC7687843 DOI: 10.1186/s13059-020-02190-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 10/27/2020] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Chromatin organizes DNA and regulates its transcriptional activity through epigenetic modifications. Heterochromatic regions of the genome are generally transcriptionally silent, while euchromatin is more prone to transcription. During DNA replication, both genetic information and chromatin modifications must be faithfully passed on to daughter strands. There is evidence that DNA polymerases play a role in transcriptional silencing, but the extent of their contribution and how it relates to heterochromatin maintenance is unclear. RESULTS We isolate a strong hypomorphic Arabidopsis thaliana mutant of the POL2A catalytic subunit of DNA polymerase epsilon and show that POL2A is required to stabilize heterochromatin silencing genome-wide, likely by preventing replicative stress. We reveal that POL2A inhibits DNA methylation and histone H3 lysine 9 methylation. Hence, the release of heterochromatin silencing in POL2A-deficient mutants paradoxically occurs in a chromatin context of increased levels of these two repressive epigenetic marks. At the nuclear level, the POL2A defect is associated with fragmentation of heterochromatin. CONCLUSION These results indicate that POL2A is critical to heterochromatin structure and function, and that unhindered replisome progression is required for the faithful propagation of DNA methylation throughout the cell cycle.
Collapse
Affiliation(s)
- Pierre Bourguet
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
| | - Leticia López-González
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
| | - Ángeles Gómez-Zambrano
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
- Present Address: Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Cartuja, Avda, Américo Vespucio, 49., 41092, Sevilla, Spain
| | - Thierry Pélissier
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
| | - Amy Hesketh
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
| | - Magdalena E Potok
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Marie-Noëlle Pouch-Pélissier
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
| | - Magali Perez
- Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRA, University Paris-Sud, University of Evry, University Paris-Diderot, Sorbonne Paris-Cite, University of Paris-Saclay, Batiment, 630, 91405, Orsay, France
| | - Olivier Da Ines
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
| | - David Latrasse
- Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRA, University Paris-Sud, University of Evry, University Paris-Diderot, Sorbonne Paris-Cite, University of Paris-Saclay, Batiment, 630, 91405, Orsay, France
| | - Charles I White
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France
| | - Steven E Jacobsen
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Moussa Benhamed
- Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRA, University Paris-Sud, University of Evry, University Paris-Diderot, Sorbonne Paris-Cite, University of Paris-Saclay, Batiment, 630, 91405, Orsay, France
| | - Olivier Mathieu
- Institute of Genetics Reproduction and Development (iGReD), Université Clermont Auvergne, CNRS, Inserm, F-63000, Clermont-Ferrand, France.
| |
Collapse
|
6
|
Polymerase δ promotes chromosomal rearrangements and imprecise double-strand break repair. Proc Natl Acad Sci U S A 2020; 117:27566-27577. [PMID: 33077594 DOI: 10.1073/pnas.2014176117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Recent studies have implicated DNA polymerases θ (Pol θ) and β (Pol β) as mediators of alternative nonhomologous end-joining (Alt-NHEJ) events, including chromosomal translocations. Here we identify subunits of the replicative DNA polymerase δ (Pol δ) as promoters of Alt-NHEJ that results in more extensive intrachromosomal mutations at a single double-strand break (DSB) and more frequent translocations between two DSBs. Depletion of the Pol δ accessory subunit POLD2 destabilizes the complex, resulting in degradation of both POLD1 and POLD3 in human cells. POLD2 depletion markedly reduces the frequency of translocations with sequence modifications but does not affect the frequency of translocations with exact joins. Using separation-of-function mutants, we show that both the DNA synthesis and exonuclease activities of the POLD1 subunit contribute to translocations. As described in yeast and unlike Pol θ, Pol δ also promotes homology-directed repair. Codepletion of POLD2 with 53BP1 nearly eliminates translocations. POLD1 and POLD2 each colocalize with phosphorylated H2AX at ionizing radiation-induced DSBs but not with 53BP1. Codepletion of POLD2 with either ligase 3 (LIG3) or ligase 4 (LIG4) does not further reduce translocation frequency compared to POLD2 depletion alone. Together, these data support a model in which Pol δ promotes Alt-NHEJ in human cells at DSBs, including translocations.
Collapse
|
7
|
Zhu Y, Hu X, Duan Y, Li S, Wang Y, Rehman AU, He J, Zhang J, Hua D, Yang L, Wang L, Chen Z, Li C, Wang B, Song CP, Sun Q, Yang S, Gong Z. The Arabidopsis Nodulin Homeobox Factor AtNDX Interacts with AtRING1A/B and Negatively Regulates Abscisic Acid Signaling. THE PLANT CELL 2020; 32:703-721. [PMID: 31919300 PMCID: PMC7054043 DOI: 10.1105/tpc.19.00604] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 12/11/2019] [Accepted: 01/03/2020] [Indexed: 05/04/2023]
Abstract
The phytohormone abscisic acid (ABA) and the Polycomb group proteins have key roles in regulating plant growth and development; however, their interplay and underlying mechanisms are not fully understood. Here, we identified an Arabidopsis (Arabidopsis thaliana) nodulin homeobox (AtNDX) protein as a negative regulator in the ABA signaling pathway. AtNDX mutants are hypersensitive to ABA, as measured by inhibition of seed germination and root growth, and the expression of AtNDX is downregulated by ABA. AtNDX interacts with the Polycomb Repressive Complex1 (PRC1) core components AtRING1A and AtRING1B in vitro and in vivo, and together, they negatively regulate the expression levels of some ABA-responsive genes. We identified ABA-INSENSITIVE (ABI4) as a direct target of AtNDX. AtNDX directly binds the downstream region of ABI4 and deleting this region increases the ABA sensitivity of primary root growth. Furthermore, ABI4 mutations rescue the ABA-hypersensitive phenotypes of ndx mutants and ABI4-overexpressing plants are hypersensitive to ABA in primary root growth. Thus, our work reveals the critical functions of AtNDX and PRC1 in some ABA-mediated processes and their regulation of ABI4.
Collapse
Affiliation(s)
- Yujuan Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
- Lingnan Guangdong Laboratory of Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, 518100, China
| | - Xiaoying Hu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Ying Duan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Shaofang Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Yu Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Amin Ur Rehman
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Junna He
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Jing Zhang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Deping Hua
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Li Yang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Li Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Zhizhong Chen
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Chuanyou Li
- State Key Laboratory of Plant Genomics, National Centre for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Baoshan Wang
- Key Lab of Plant Stress Research, College of Life Science, Shandong Normal University, Ji'nan, 250000, China
| | - Chun-Peng Song
- Collaborative Innovation Center of Crop Stress Biology, Henan Province, Institute of Plant Stress Biology, Henan University, Kaifeng, 475001, China
| | - Qianwen Sun
- Center for Plant Biology and Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Shuhua Yang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Zhizhong Gong
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| |
Collapse
|
8
|
Abstract
Maintenance of genome integrity is a key process in all organisms. DNA polymerases (Pols) are central players in this process as they are in charge of the faithful reproduction of the genetic information, as well as of DNA repair. Interestingly, all eukaryotes possess a large repertoire of polymerases. Three protein complexes, DNA Pol α, δ, and ε, are in charge of nuclear DNA replication. These enzymes have the fidelity and processivity required to replicate long DNA sequences, but DNA lesions can block their progression. Consequently, eukaryotic genomes also encode a variable number of specialized polymerases (between five and 16 depending on the organism) that are involved in the replication of damaged DNA, DNA repair, and organellar DNA replication. This diversity of enzymes likely stems from their ability to bypass specific types of lesions. In the past 10–15 years, our knowledge regarding plant DNA polymerases dramatically increased. In this review, we discuss these recent findings and compare acquired knowledge in plants to data obtained in other eukaryotes. We also discuss the emerging links between genome and epigenome replication.
Collapse
|
9
|
Peroxisomal β-oxidation regulates histone acetylation and DNA methylation in Arabidopsis. Proc Natl Acad Sci U S A 2019; 116:10576-10585. [PMID: 31064880 DOI: 10.1073/pnas.1904143116] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Epigenetic markers, such as histone acetylation and DNA methylation, determine chromatin organization. In eukaryotic cells, metabolites from organelles or the cytosol affect epigenetic modifications. However, the relationships between metabolites and epigenetic modifications are not well understood in plants. We found that peroxisomal acyl-CoA oxidase 4 (ACX4), an enzyme in the fatty acid β-oxidation pathway, is required for suppressing the silencing of some endogenous loci, as well as Pro35S:NPTII in the ProRD29A:LUC/C24 transgenic line. The acx4 mutation reduces nuclear histone acetylation and increases DNA methylation at the NOS terminator of Pro35S:NPTII and at some endogenous genomic loci, which are also targeted by the demethylation enzyme REPRESSOR OF SILENCING 1 (ROS1). Furthermore, mutations in multifunctional protein 2 (MFP2) and 3-ketoacyl-CoA thiolase-2 (KAT2/PED1/PKT3), two enzymes in the last two steps of the β-oxidation pathway, lead to similar patterns of DNA hypermethylation as in acx4 Thus, metabolites from fatty acid β-oxidation in peroxisomes are closely linked to nuclear epigenetic modifications, which may affect diverse cellular processes in plants.
Collapse
|
10
|
Li J, Liang W, Li Y, Qian W. APURINIC/APYRIMIDINIC ENDONUCLEASE2 and ZINC FINGER DNA 3'-PHOSPHOESTERASE Play Overlapping Roles in the Maintenance of Epigenome and Genome Stability. THE PLANT CELL 2018; 30:1954-1970. [PMID: 30135084 PMCID: PMC6181018 DOI: 10.1105/tpc.18.00287] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 07/19/2018] [Accepted: 08/22/2018] [Indexed: 05/21/2023]
Abstract
Base excision repair (BER) is essential for active DNA demethylation and DNA damage repair in mammals and plants. Here, we provide genetic and biochemical evidence that APURINIC/APYRIMIDINIC ENDONUCLEASE2 (APE2) plays overlapping roles with ZINC FINGER DNA 3'-PHOSPHOESTERASE (ZDP) in active DNA demethylation and DNA damage repair in Arabidopsis thaliana Simultaneous mutation of APE2 and ZDP causes DNA hypermethylation at more than 2000 loci, most of which are not hypermethylated in ape2 or zdp single mutants. The zdp and ape2 single mutants exhibit normal development, but the zdp ape2 double mutants display pleiotropic developmental defects and are supersensitive to the DNA alkylating reagent methyl methanesulfonate. The gradual accumulation of DNA lesions in the zdp ape2 seedlings is accompanied by constitutive activation of the DNA damage response and alteration of the cell cycle. Interestingly, knockout of the key DNA demethylase REPRESSOR OF SILENCING1 reduces the magnitude of DNA lesion accumulation and the DNA damage response in the zdp ape2 mutants, suggesting that a proportion of the DNA damage in the zdp ape2 mutants arises from incomplete active DNA demethylation. Lastly, we find that APE2 has 3'-phosphatase activity and strong 3'-5' exonuclease activity in vitro. Together, our results suggest that APE2 and ZDP, two BER proteins, play overlapping roles in the maintenance of epigenome and genome stability in plants.
Collapse
Affiliation(s)
- Jinchao Li
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| | - Wenjie Liang
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| | - Yan Li
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Weiqiang Qian
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| |
Collapse
|
11
|
Vergara Z, Gutierrez C. Emerging roles of chromatin in the maintenance of genome organization and function in plants. Genome Biol 2017; 18:96. [PMID: 28535770 PMCID: PMC5440935 DOI: 10.1186/s13059-017-1236-9] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chromatin is not a uniform macromolecular entity; it contains different domains characterized by complex signatures of DNA and histone modifications. Such domains are organized both at a linear scale along the genome and spatially within the nucleus. We discuss recent discoveries regarding mechanisms that establish boundaries between chromatin states and nuclear territories. Chromatin organization is crucial for genome replication, transcriptional silencing, and DNA repair and recombination. The replication machinery is relevant for the maintenance of chromatin states, influencing DNA replication origin specification and accessibility. Current studies reinforce the idea of intimate crosstalk between chromatin features and processes involving DNA transactions.
Collapse
Affiliation(s)
- Zaida Vergara
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049, Madrid, Spain
| | - Crisanto Gutierrez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Nicolas Cabrera 1, Cantoblanco, 28049, Madrid, Spain.
| |
Collapse
|