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Zhang Z, Liang C, Ren Y, Lv Z, Huang J. Interaction of ubiquitin-like protein SILENCING DEFECTIVE 2 with LIKE HETEROCHROMATIN PROTEIN 1 is required for regulation of anthocyanin biosynthesis in Arabidopsis thaliana in response to sucrose. THE NEW PHYTOLOGIST 2024; 243:1374-1386. [PMID: 38558017 DOI: 10.1111/nph.19725] [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: 12/23/2023] [Accepted: 03/13/2024] [Indexed: 04/04/2024]
Abstract
The regulatory mechanisms of anthocyanin biosynthesis have been well documented at the transcriptional and translational levels. By contrast, how anthocyanin biosynthesis is epigenetically regulated remains largely unknown. In this study, we employed genetic, molecular biology, and chromatin immunoprecipitation-quantitative polymerase chain reaction assays to identify a regulatory module essential for repressing the expression of genes involved in anthocyanin biosynthesis through chromatin remodeling. We found that SILENCING DEFECTIVE 2 (SDE2), which was previously identified as a negative regulator for sucrose-induced anthocyanin accumulation in Arabidopsis, is cleaved into N-terminal SDE2-UBL and C-terminal SDE2-C fragments at the first diglycine motif, and the cleaved SDE2-C, which can fully complement the sde2 mutant, is localized in the nucleus and physically interacts with LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) in vitro and in vivo. Genetic analyses showed that both SDE2 and LHP1 act as negative factors for anthocyanin biosynthesis. Consistently, immunoblot analysis revealed that the level of LHP1-bound histone H3 lysine 27 trimethylation (H3K27me3) significantly decreases in sde2 and lhp1 mutants, compared to wild-type (WT). In addition, we found that sugar can induce expression of SDE2 and LHP1, and enhance the level of the nucleus-localized SDE2-C. Taken together, our data suggest that the SDE2-C-LHP1 module is required for repression of gene expression through H3K27me3 modification during sugar-induced anthocyanin biosynthesis in Arabidopsis thaliana.
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Affiliation(s)
- Zhiyi Zhang
- Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Chengcheng Liang
- Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Yulong Ren
- Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Zhaojun Lv
- Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Jirong Huang
- Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai, 200234, China
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2
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Harada N, Asada S, Jiang L, Nguyen H, Moreau L, Marina RJ, Adelman K, Iyer DR, D'Andrea AD. The splicing factor CCAR1 regulates the Fanconi anemia/BRCA pathway. Mol Cell 2024; 84:2618-2633.e10. [PMID: 39025073 DOI: 10.1016/j.molcel.2024.06.031] [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: 09/06/2023] [Revised: 05/15/2024] [Accepted: 06/25/2024] [Indexed: 07/20/2024]
Abstract
The twenty-three Fanconi anemia (FA) proteins cooperate in the FA/BRCA pathway to repair DNA interstrand cross-links (ICLs). The cell division cycle and apoptosis regulator 1 (CCAR1) protein is also a regulator of ICL repair, though its possible function in the FA/BRCA pathway remains unknown. Here, we demonstrate that CCAR1 plays a unique upstream role in the FA/BRCA pathway and is required for FANCA protein expression in human cells. Interestingly, CCAR1 co-immunoprecipitates with FANCA pre-mRNA and is required for FANCA mRNA processing. Loss of CCAR1 results in retention of a poison exon in the FANCA transcript, thereby leading to reduced FANCA protein expression. A unique domain of CCAR1, the EF hand domain, is required for interaction with the U2AF heterodimer of the spliceosome and for excision of the poison exon. Taken together, CCAR1 is a splicing modulator required for normal splicing of the FANCA mRNA and other mRNAs involved in various cellular pathways.
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Affiliation(s)
- Naoya Harada
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Shuhei Asada
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Lige Jiang
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Huy Nguyen
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Lisa Moreau
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Ryan J Marina
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Karen Adelman
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Divya R Iyer
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA.
| | - Alan D D'Andrea
- Division of Radiation and Genome Stability, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA.
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3
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Saldanha J, Rageul J, Patel J, Phi A, Lo N, Park J, Kim H. The TIMELESS and PARP1 interaction suppresses replication-associated DNA gap accumulation. Nucleic Acids Res 2024; 52:6424-6440. [PMID: 38801073 PMCID: PMC11194094 DOI: 10.1093/nar/gkae445] [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: 01/03/2024] [Revised: 04/09/2024] [Accepted: 05/10/2024] [Indexed: 05/29/2024] Open
Abstract
TIMELESS (TIM) in the fork protection complex acts as a scaffold of the replisome to prevent its uncoupling and ensure efficient DNA replication fork progression. Nevertheless, its underlying basis for coordinating leading and lagging strand synthesis to limit single-stranded DNA (ssDNA) exposure remains elusive. Here, we demonstrate that acute degradation of TIM at ongoing DNA replication forks induces the accumulation of ssDNA gaps stemming from defective Okazaki fragment (OF) processing. Cells devoid of TIM fail to support the poly(ADP-ribosyl)ation necessary for backing up the canonical OF processing mechanism mediated by LIG1 and FEN1. Consequently, recruitment of XRCC1, a known effector of PARP1-dependent single-strand break repair, to post-replicative ssDNA gaps behind replication forks is impaired. Physical disruption of the TIM-PARP1 complex phenocopies the rapid loss of TIM, indicating that the TIM-PARP1 interaction is critical for the activation of this compensatory pathway. Accordingly, combined deficiency of FEN1 and the TIM-PARP1 interaction leads to synergistic DNA damage and cytotoxicity. We propose that TIM is essential for the engagement of PARP1 to the replisome to coordinate lagging strand synthesis with replication fork progression. Our study identifies TIM as a synthetic lethal target of OF processing enzymes that can be exploited for cancer therapy.
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Affiliation(s)
- Joanne Saldanha
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
- The Graduate program in Genetics, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Julie Rageul
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Jinal A Patel
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Amy L Phi
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Natalie Lo
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Jennifer J Park
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Hyungjin Kim
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
- The Graduate program in Genetics, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
- Stony Brook Cancer Center, Renaissance School of Medicine at Stony Brook University, Stony Brook, NY 11794, USA
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4
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Marshall S, Navarro MV, Ascenҫão CF, Smolka MB. IN-DEPTH MAPPING OF DNA-PKcs SIGNALING UNCOVERS CONSERVED FEATURES OF ITS KINASE SPECIFICITY. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.17.576037. [PMID: 38293078 PMCID: PMC10827184 DOI: 10.1101/2024.01.17.576037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
DNA-PKcs is a DNA damage sensor kinase with established roles in DNA double-strand break repair via non-homologous end joining. Recent studies have revealed additional roles of DNA-PKcs in the regulation of transcription, translation and DNA replication. However, the substrates through which DNA-PKcs regulates these processes remain largely undefined. Here we utilized quantitative phosphoproteomics to generate a high coverage map of DNA-PKcs signaling in response to ionizing radiation and mapped its interplay with the ATM kinase. Beyond the detection of the canonical S/T-Q phosphorylation motif, we uncovered a non-canonical mode of DNA-PKcs signaling targeting S/T-ψ-D/E motifs. Cross-species analysis in mouse pre-B and human HCT116 cell lines revealed splicing factors and transcriptional regulators phosphorylated at this novel motif, several of which contain SAP domains. These findings expand the list of DNA-PKcs and ATM substrates and establish a novel preferential phosphorylation motif for DNA-PKcs that connects it to proteins involved in nucleotide processes and interactions.
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Affiliation(s)
- Shannon Marshall
- 1. Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Marcos V.A.S. Navarro
- 1. Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
- 2. IFSC Institute of Physics of São Carlos, University of São Paulo, São Carlos - SP, 13566-590, Brazil
| | - Carolline F.R. Ascenҫão
- 1. Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Marcus B. Smolka
- 1. Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
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5
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Vipat S, Moiseeva TN. The TIMELESS Roles in Genome Stability and Beyond. J Mol Biol 2024; 436:168206. [PMID: 37481157 DOI: 10.1016/j.jmb.2023.168206] [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: 05/01/2023] [Revised: 06/20/2023] [Accepted: 07/12/2023] [Indexed: 07/24/2023]
Abstract
TIMELESS protein (TIM) protects replication forks from stalling at difficult-to-replicate regions and plays an important role in DNA damage response, including checkpoint signaling, protection of stalled replication forks and DNA repair. Loss of TIM causes severe replication stress, while its overexpression is common in various types of cancer, providing protection from DNA damage and resistance to chemotherapy. Although TIM has mostly been studied for its part in replication stress response, its additional roles in supporting genome stability and a wide variety of other cellular pathways are gradually coming to light. This review discusses the diverse functions of TIM and its orthologs in healthy and cancer cells, open questions, and potential future directions.
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Affiliation(s)
- Sameera Vipat
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Tallinn 12618, Estonia
| | - Tatiana N Moiseeva
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Tallinn 12618, Estonia.
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Patel JA, Zezelic C, Rageul J, Saldanha J, Khan A, Kim H. Replisome dysfunction upon inducible TIMELESS degradation synergizes with ATR inhibition to trigger replication catastrophe. Nucleic Acids Res 2023; 51:6246-6263. [PMID: 37144518 PMCID: PMC10325925 DOI: 10.1093/nar/gkad363] [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: 01/03/2023] [Revised: 03/29/2023] [Accepted: 04/26/2023] [Indexed: 05/06/2023] Open
Abstract
The structure of DNA replication forks is preserved by TIMELESS (TIM) in the fork protection complex (FPC) to support seamless fork progression. While the scaffolding role of the FPC to couple the replisome activity is much appreciated, the detailed mechanism whereby inherent replication fork damage is sensed and counteracted during DNA replication remains largely elusive. Here, we implemented an auxin-based degron system that rapidly triggers inducible proteolysis of TIM as a source of endogenous DNA replication stress and replisome dysfunction to dissect the signaling events that unfold at stalled forks. We demonstrate that acute TIM degradation activates the ATR-CHK1 checkpoint, whose inhibition culminates in replication catastrophe by single-stranded DNA accumulation and RPA exhaustion. Mechanistically, unrestrained replisome uncoupling, excessive origin firing, and aberrant reversed fork processing account for the synergistic fork instability. Simultaneous TIM loss and ATR inactivation triggers DNA-PK-dependent CHK1 activation, which is unexpectedly necessary for promoting fork breakage by MRE11 and catastrophic cell death. We propose that acute replisome dysfunction results in a hyper-dependency on ATR to activate local and global fork stabilization mechanisms to counteract irreversible fork collapse. Our study identifies TIM as a point of replication vulnerability in cancer that can be exploited with ATR inhibitors.
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Affiliation(s)
- Jinal A Patel
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Camryn Zezelic
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Julie Rageul
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Joanne Saldanha
- The Graduate program in Genetics, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Arafat Khan
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Hyungjin Kim
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
- Stony Brook Cancer Center, Renaissance School of Medicine at Stony Brook University, Stony Brook, NY 11794, USA
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7
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Saldanha J, Rageul J, Patel JA, Kim H. The Adaptive Mechanisms and Checkpoint Responses to a Stressed DNA Replication Fork. Int J Mol Sci 2023; 24:10488. [PMID: 37445667 PMCID: PMC10341514 DOI: 10.3390/ijms241310488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/13/2023] [Accepted: 06/20/2023] [Indexed: 07/15/2023] Open
Abstract
DNA replication is a tightly controlled process that ensures the faithful duplication of the genome. However, DNA damage arising from both endogenous and exogenous assaults gives rise to DNA replication stress associated with replication fork slowing or stalling. Therefore, protecting the stressed fork while prompting its recovery to complete DNA replication is critical for safeguarding genomic integrity and cell survival. Specifically, the plasticity of the replication fork in engaging distinct DNA damage tolerance mechanisms, including fork reversal, repriming, and translesion DNA synthesis, enables cells to overcome a variety of replication obstacles. Furthermore, stretches of single-stranded DNA generated upon fork stalling trigger the activation of the ATR kinase, which coordinates the cellular responses to replication stress by stabilizing the replication fork, promoting DNA repair, and controlling cell cycle and replication origin firing. Deregulation of the ATR checkpoint and aberrant levels of chronic replication stress is a common characteristic of cancer and a point of vulnerability being exploited in cancer therapy. Here, we discuss the various adaptive responses of a replication fork to replication stress and the roles of ATR signaling that bring fork stabilization mechanisms together. We also review how this knowledge is being harnessed for the development of checkpoint inhibitors to trigger the replication catastrophe of cancer cells.
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Affiliation(s)
- Joanne Saldanha
- The Graduate Program in Genetics, Stony Brook University, Stony Brook, NY 11794, USA
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - Julie Rageul
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - Jinal A Patel
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - Hyungjin Kim
- The Graduate Program in Genetics, Stony Brook University, Stony Brook, NY 11794, USA
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
- Stony Brook Cancer Center, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY 11794, USA
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8
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Patel JA, Kim H. The TIMELESS effort for timely DNA replication and protection. Cell Mol Life Sci 2023; 80:84. [PMID: 36892674 PMCID: PMC9998586 DOI: 10.1007/s00018-023-04738-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 02/16/2023] [Accepted: 02/24/2023] [Indexed: 03/10/2023]
Abstract
Accurate replication of the genome is fundamental to cellular survival and tumor prevention. The DNA replication fork is vulnerable to DNA lesions and damages that impair replisome progression, and improper control over DNA replication stress inevitably causes fork stalling and collapse, a major source of genome instability that fuels tumorigenesis. The integrity of the DNA replication fork is maintained by the fork protection complex (FPC), in which TIMELESS (TIM) constitutes a key scaffold that couples the CMG helicase and replicative polymerase activities, in conjunction with its interaction with other proteins associated with the replication machinery. Loss of TIM or the FPC in general results in impaired fork progression, elevated fork stalling and breakage, and a defect in replication checkpoint activation, thus underscoring its pivotal role in protecting the integrity of both active and stalled replication forks. TIM is upregulated in multiple cancers, which may represent a replication vulnerability of cancer cells that could be exploited for new therapies. Here, we discuss recent advances on our understanding of the multifaceted roles of TIM in DNA replication and stalled fork protection, and how its complex functions are engaged in collaboration with other genome surveillance and maintenance factors.
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Affiliation(s)
- Jinal A Patel
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Basic Sciences Tower 8-125, 101 Nicolls Rd, Stony Brook, NY, 11794, USA
| | - Hyungjin Kim
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Basic Sciences Tower 8-125, 101 Nicolls Rd, Stony Brook, NY, 11794, USA.
- Stony Brook Cancer Center and Renaissance School of Medicine, Stony Brook University, Basic Sciences Tower 8-125, 101 Nicolls Rd, Stony Brook, NY, 11794, USA.
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9
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Korn SM, Von Ehr J, Dhamotharan K, Tants JN, Abele R, Schlundt A. Insight into the Structural Basis for Dual Nucleic Acid-Recognition by the Scaffold Attachment Factor B2 Protein. Int J Mol Sci 2023; 24:ijms24043286. [PMID: 36834708 PMCID: PMC9958909 DOI: 10.3390/ijms24043286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/30/2023] [Accepted: 02/03/2023] [Indexed: 02/10/2023] Open
Abstract
The family of scaffold attachment factor B (SAFB) proteins comprises three members and was first identified as binders of the nuclear matrix/scaffold. Over the past two decades, SAFBs were shown to act in DNA repair, mRNA/(l)ncRNA processing and as part of protein complexes with chromatin-modifying enzymes. SAFB proteins are approximately 100 kDa-sized dual nucleic acid-binding proteins with dedicated domains in an otherwise largely unstructured context, but whether and how they discriminate DNA and RNA binding has remained enigmatic. We here provide the SAFB2 DNA- and RNA-binding SAP and RRM domains in their functional boundaries and use solution NMR spectroscopy to ascribe DNA- and RNA-binding functions. We give insight into their target nucleic acid preferences and map the interfaces with respective nucleic acids on sparse data-derived SAP and RRM domain structures. Further, we provide evidence that the SAP domain exhibits intra-domain dynamics and a potential tendency to dimerize, which may expand its specifically targeted DNA sequence range. Our data provide a first molecular basis of and a starting point towards deciphering DNA- and RNA-binding functions of SAFB2 on the molecular level and serve a basis for understanding its localization to specific regions of chromatin and its involvement in the processing of specific RNA species.
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Affiliation(s)
- Sophie M. Korn
- Institute for Molecular Biosciences, Biomolecular Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
| | - Julian Von Ehr
- Institute for Molecular Biosciences, Biomolecular Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
- IMPRS on Cellular Biophysics, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
| | - Karthikeyan Dhamotharan
- Institute for Molecular Biosciences, Biomolecular Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
| | - Jan-Niklas Tants
- Institute for Molecular Biosciences, Biomolecular Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
| | - Rupert Abele
- Institute for Biochemistry, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Andreas Schlundt
- Institute for Molecular Biosciences, Biomolecular Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
- Correspondence:
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10
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Anil AT, Choudhary K, Pandian R, Gupta P, Thakran P, Singh A, Sharma M, Mishra SK. Splicing of branchpoint-distant exons is promoted by Cactin, Tls1 and the ubiquitin-fold-activated Sde2. Nucleic Acids Res 2022; 50:10000-10014. [PMID: 36095128 PMCID: PMC9508853 DOI: 10.1093/nar/gkac769] [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: 07/21/2022] [Revised: 08/22/2022] [Accepted: 08/27/2022] [Indexed: 11/13/2022] Open
Abstract
Intron diversity facilitates regulated gene expression and alternative splicing. Spliceosomes excise introns after recognizing their splicing signals: the 5'-splice site (5'ss), branchpoint (BP) and 3'-splice site (3'ss). The latter two signals are recognized by U2 small nuclear ribonucleoprotein (snRNP) and its accessory factors (U2AFs), but longer spacings between them result in weaker splicing. Here, we show that excision of introns with a BP-distant 3'ss (e.g. rap1 intron 2) requires the ubiquitin-fold-activated splicing regulator Sde2 in Schizosaccharomyces pombe. By monitoring splicing-specific ura4 reporters in a collection of S. pombe mutants, Cay1 and Tls1 were identified as additional regulators of this process. The role of Sde2, Cay1 and Tls1 was further confirmed by increasing BP-3'ss spacings in a canonical tho5 intron. We also examined BP-distant exons spliced independently of these factors and observed that RNA secondary structures possibly bridged the gap between the two signals. These proteins may guide the 3'ss towards the spliceosome's catalytic centre by folding the RNA between the BP and 3'ss. Orthologues of Sde2, Cay1 and Tls1, although missing in the intron-poor Saccharomyces cerevisiae, are present in intron-rich eukaryotes, including humans. This type of intron-specific pre-mRNA splicing appears to have evolved for regulated gene expression and alternative splicing of key heterochromatin factors.
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Affiliation(s)
- Anupa T Anil
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Karan Choudhary
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Rakesh Pandian
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Praver Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Poonam Thakran
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Arashdeep Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Monika Sharma
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Shravan Kumar Mishra
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
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