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Shiekh S, Feldt D, Jack A, Kodikara SG, Alfehaid J, Pasha S, Yildiz A, Balci H. Protection of the Telomeric Junction by the Shelterin Complex. J Am Chem Soc 2024; 146:25158-25165. [PMID: 39207958 PMCID: PMC11404488 DOI: 10.1021/jacs.4c08649] [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] [Indexed: 09/04/2024]
Abstract
Shelterin serves critical roles in suppressing superfluous DNA damage repair pathways on telomeres. The junction between double-stranded telomeric tracts (dsTEL) and single-stranded telomeric overhang (ssTEL) is the most accessible region of the telomeric DNA. The shelterin complex contains dsTEL and ssTEL binding proteins and can protect this junction by bridging the ssTEL and dsTEL tracts. To test this possibility, we monitored shelterin binding to telomeric DNA substrates with varying ssTEL and dsTEL lengths and quantified its impact on telomere accessibility using single-molecule fluorescence microscopy methods in vitro. We identified the first dsTEL repeat nearest the junction as the preferred binding site for creating the shelterin bridge. Shelterin requires at least two ssTEL repeats, while the POT1 subunit of shelterin that binds to ssTEL requires longer ssTEL tracts for stable binding to telomeres and effective protection of the junction region. The ability of POT1 to protect the junction is significantly enhanced by the 5'-phosphate at the junction. Collectively, our results show that shelterin enhances the binding stability of POT1 to ssTEL and provides more effective protection compared with POT1 alone by bridging single- and double-stranded telomeric tracts.
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Affiliation(s)
- Sajad Shiekh
- Department of Physics, Kent State University, Kent, Ohio 44242, United States
| | - Darion Feldt
- Department of Physics, Kent State University, Kent, Ohio 44242, United States
| | - Amanda Jack
- Biophysics Graduate Group, University of California, Berkeley, California 94720, United States
| | - Sineth G Kodikara
- Department of Physics, Kent State University, Kent, Ohio 44242, United States
| | - Janan Alfehaid
- Department of Physics, Kent State University, Kent, Ohio 44242, United States
| | - Sabaha Pasha
- Department of Physics, Kent State University, Kent, Ohio 44242, United States
| | - Ahmet Yildiz
- Biophysics Graduate Group, University of California, Berkeley, California 94720, United States
- Physics Department, University of California, Berkeley, California 94720, United States
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
| | - Hamza Balci
- Department of Physics, Kent State University, Kent, Ohio 44242, United States
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2
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Shiekh S, Feldt D, Jack A, Kodikara SG, Alfehaid J, Pasha S, Yildiz A, Balci H. Protection of the Telomeric Junction by the Shelterin Complex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.18.608453. [PMID: 39229120 PMCID: PMC11370466 DOI: 10.1101/2024.08.18.608453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
Shelterin serves critical roles in suppressing superfluous DNA damage repair pathways on telomeres. The junction between double-stranded telomeric tracts (dsTEL) and single-stranded telomeric overhang (ssTEL) is the most accessible region of the telomeric DNA. The shelterin complex contains dsTEL and ssTEL binding proteins and can protect this junction by bridging between the ssTEL and dsTEL tracts. To test this possibility, we monitored shelterin binding to telomeric DNA substrates with varying ssTEL and dsTEL lengths and quantified its impact on telomere accessibility using single-molecule fluorescence microscopy methods in vitro. We identified the first dsTEL repeat nearest to the junction as the preferred binding site for creating the shelterin bridge. Shelterin requires at least two ssTEL repeats while the POT1 subunit of shelterin that binds to ssTEL requires longer ssTEL tracts for stable binding to telomeres and effective protection of the junction region. The ability of POT1 to protect the junction is significantly enhanced by the 5'-phosphate at the junction. Collectively, our results show that shelterin enhances the binding stability of POT1 to ssTEL and provides more effective protection compared to POT1 alone by bridging single- and double-stranded telomeric tracts.
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Affiliation(s)
- Sajad Shiekh
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Darion Feldt
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Amanda Jack
- Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
| | | | - Janan Alfehaid
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Sabaha Pasha
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Ahmet Yildiz
- Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
- Physics Department, University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Hamza Balci
- Department of Physics, Kent State University, Kent, OH 44242, USA
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3
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Yang K, Alkhamis O, Canoura J, Bryant A, Gong EM, Barbu M, Taylor S, Nikic D, Banerjee S, Xiao Y, Stojanovic MN, Landry DW. Exploring the Landscape of Aptamers: From Cross-Reactive to Selective to Specific, High-Affinity Receptors for Cocaine. JACS AU 2024; 4:760-770. [PMID: 38425914 PMCID: PMC10900216 DOI: 10.1021/jacsau.3c00781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 01/25/2024] [Accepted: 01/25/2024] [Indexed: 03/02/2024]
Abstract
We reported over 20 years ago MNS-4.1, the first DNA aptamer with a micromolar affinity for cocaine. MNS-4.1 is based on a structural motif that is very common in any random pool of oligonucleotides, and it is actually a nonspecific hydrophobic receptor with wide cross-reactivity with alkaloids and steroids. Despite such weaknesses preventing broad applications, this aptamer became widely used in proof-of-concept demonstrations of new formats of biosensors. We now report a series of progressively improved DNA aptamers recognizing cocaine, with the final optimized receptors having low nanomolar affinity and over a thousand-fold selectivity over the initial cross-reactants. In the process of optimization, we tested different methods to eliminate cross-reactivities and improve affinity, eventually achieving properties that are comparable to those of the reported monoclonal antibody candidates for the therapy of overdose. Multiple aptamers that we now report share structural motifs with the previously reported receptor for serotonin. Further mutagenesis studies revealed a palindromic, highly adaptable, broadly cross-reactive hydrophobic motif that could be rebuilt through mutagenesis, expansion of linker regions, and selections into receptors with exceptional affinities and varying specificities.
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Affiliation(s)
- Kyungae Yang
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
| | - Obtin Alkhamis
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Juan Canoura
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Alexandra Bryant
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Edward M. Gong
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
| | - Mihaela Barbu
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
| | - Steven Taylor
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
| | - Dragan Nikic
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
| | - Saswata Banerjee
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
| | - Yi Xiao
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Milan N. Stojanovic
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
- Departments
of Biomedical Engineering and Systems Biology, Columbia University, New York, New York 10032, United States
| | - Donald W. Landry
- Department
of Medicine, Columbia University Irving
Medical Center, New York, New York 10032, United States
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4
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Zheng YY, Dartawan R, Wu Y, Wu C, Zhang H, Lu J, Hu A, Vangaveti S, Sheng J. Structural effects of inosine substitution in telomeric DNA quadruplex. Front Chem 2024; 12:1330378. [PMID: 38312345 PMCID: PMC10834636 DOI: 10.3389/fchem.2024.1330378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 01/08/2024] [Indexed: 02/06/2024] Open
Abstract
The telomeric DNA, a distal region of eukaryotic chromosome containing guanine-rich repetitive sequence of (TTAGGG)n, has been shown to adopt higher-order structures, specifically G-quadruplexes (G4s). Previous studies have demonstrated the implication of G4 in tumor inhibition through chromosome maintenance and manipulation of oncogene expression featuring their G-rich promoter regions. Besides higher order structures, several regulatory roles are attributed to DNA epigenetic markers. In this work, we investigated how the structural dynamics of a G-quadruplex, formed by the telomeric sequence, is affected by inosine, a prevalent modified nucleotide. We used the standard (TTAGGG)n telomere repeats with guanosine mutated to inosine at each G position. Sequences (GGG)4, (IGG)4, (GIG)4, (GGI)4, (IGI)4, (IIG)4, (GII)4, and (III)4, bridged by TTA linker, are studied using biophysical experiments and molecular modeling. The effects of metal cations in quadruplex folding were explored in both Na+ and K+ containing buffers using CD and UV-melting studies. Our results show that antiparallel quadruplex topology forms with the native sequence (GGG)4 and the terminal modified DNAs (IGG)4 and (GGI)4 in both Na+ and K+ containing buffers. Specifically, quadruplex hybrid was observed for (GGG)4 in K+ buffer. Among the other modified sequences, (GIG)4, (IGI)4 and (GII)4 show parallel features, while (IIG)4 and (III)4 show no detectable conformation in the presence of either Na+ or K+. Our studies indicate that terminal lesions (IGG)4 and (GGI)4 may induce certain unknown conformations. The folding dynamics become undetectable in the presence of more than one inosine substitution except (IGI)4 in both buffer ions. In addition, both UV melting and CD melting studies implied that in most cases the K+ cation confers more thermodynamic stability compared to Na+. Collectively, our conformational studies revealed the diverse structural polymorphisms of G4 with position dependent G-to-I mutations in different ion conditions.
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Affiliation(s)
- Ya Ying Zheng
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Ricky Dartawan
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Yuhan Wu
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Chengze Wu
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Hope Zhang
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Jeanne Lu
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Ashley Hu
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Sweta Vangaveti
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
| | - Jia Sheng
- Department of Chemistry, Albany, NY, United States
- The RNA Institute, University at Albany, State University of New York, Albany, NY, United States
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Shiekh S, Kodikara SG, Balci H. Structure, Topology, and Stability of Multiple G-quadruplexes in Long Telomeric Overhangs. J Mol Biol 2024; 436:168205. [PMID: 37481156 PMCID: PMC10799177 DOI: 10.1016/j.jmb.2023.168205] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 07/05/2023] [Accepted: 07/12/2023] [Indexed: 07/24/2023]
Abstract
Telomeres and their single stranded overhangs gradually shorten with successive cell divisions, as part of the natural aging process, but can be elongated by telomerase, a nucleoprotein complex which is activated in the majority of cancers. This prominent implication in cancer and aging has made the repetitive telomeric sequences (TTAGGG repeats) and the G-quadruplex structures that form in their overhangs the focus of intense research in the past several decades. However, until recently most in vitro efforts to understand the structure, stability, dynamics, and interactions of telomeric overhangs had been focused on short sequences that are not representative of longer sequences encountered in a physiological setting. In this review, we will provide a broad perspective about telomeres and associated factors, and introduce the agents and structural characteristics involved in organizing, maintaining, and protecting telomeric DNA. We will also present a summary of recent research performed on long telomeric sequences, nominally defined as those that can form two or more tandem G-quadruplexes, i.e., which contain eight or more TTAGGG repeats. Results of experimental studies using a broad array of experimental tools, in addition to recent computational efforts will be discussed, particularly in terms of their implications for the stability, folding topology, and compactness of the tandem G-quadruplexes that form in long telomeric overhangs.
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Affiliation(s)
- Sajad Shiekh
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | | | - Hamza Balci
- Department of Physics, Kent State University, Kent, OH 44242, USA.
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6
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Kristoffersen E, Coletta A, Lund L, Schiøtt B, Birkedal V. Inhibited complete folding of consecutive human telomeric G-quadruplexes. Nucleic Acids Res 2023; 51:1571-1582. [PMID: 36715345 PMCID: PMC9976873 DOI: 10.1093/nar/gkad004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 12/24/2022] [Accepted: 01/04/2023] [Indexed: 01/31/2023] Open
Abstract
Noncanonical DNA structures, termed G-quadruplexes, are present in human genomic DNA and are important elements in many DNA metabolic processes. Multiple sites in the human genome have G-rich DNA stretches able to support formation of several consecutive G-quadruplexes. One of those sites is the telomeric overhang region that has multiple repeats of TTAGGG and is tightly associated with both cancer and aging. We investigated the folding of consecutive G-quadruplexes in both potassium- and sodium-containing solutions using single-molecule FRET spectroscopy, circular dichroism, thermal melting and molecular dynamics simulations. Our observations show coexistence of partially and fully folded DNA, the latter consisting of consecutive G-quadruplexes. Following the folding process over hours in sodium-containing buffers revealed fast G-quadruplex folding but slow establishment of thermodynamic equilibrium. We find that full consecutive G-quadruplex formation is inhibited by the many DNA structures randomly nucleating on the DNA, some of which are off-path conformations that need to unfold to allow full folding. Our study allows describing consecutive G-quadruplex formation in both nonequilibrium and equilibrium conditions by a unified picture, where, due to the many possible DNA conformations, full folding with consecutive G-quadruplexes as beads on a string is not necessarily achieved.
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Affiliation(s)
- Emil Laust Kristoffersen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
| | - Andrea Coletta
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus, Denmark
| | - Line Mørkholt Lund
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
| | - Birgit Schiøtt
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark,Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus, Denmark
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7
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Structural Polymorphism of Guanine Quadruplex-Containing Regions in Human Promoters. Int J Mol Sci 2022; 23:ijms232416020. [PMID: 36555662 PMCID: PMC9786302 DOI: 10.3390/ijms232416020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 12/05/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
Intramolecular guanine quadruplexes (G4s) are non-canonical nucleic acid structures formed by four guanine (G)-rich tracts that assemble into a core of stacked planar tetrads. G4-forming DNA sequences are enriched in gene promoters and are implicated in the control of gene expression. Most G4-forming DNA contains more G residues than can simultaneously be incorporated into the core resulting in a variety of different possible G4 structures. Although this kind of structural polymorphism is well recognized in the literature, there remain unanswered questions regarding possible connections between G4 polymorphism and biological function. Here we report a detailed bioinformatic survey of G4 polymorphism in human gene promoter regions. Our analysis is based on identifying G4-containing regions (G4CRs), which we define as stretches of DNA in which every residue can form part of a G4. We found that G4CRs with higher degrees of polymorphism are more tightly clustered near transcription sites and tend to contain G4s with shorter loops and bulges. Furthermore, we found that G4CRs with well-characterized biological functions tended to be longer and more polymorphic than genome-wide averages. These results represent new evidence linking G4 polymorphism to biological function and provide new criteria for identifying biologically relevant G4-forming regions from genomic data.
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8
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Shiekh S, Jack A, Saurabh A, Mustafa G, Kodikara S, Gyawali P, Hoque M, Pressé S, Yildiz A, Balci H. Shelterin reduces the accessibility of telomeric overhangs. Nucleic Acids Res 2022; 50:12885-12895. [PMID: 36511858 PMCID: PMC9825182 DOI: 10.1093/nar/gkac1176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 10/25/2022] [Accepted: 11/25/2022] [Indexed: 12/15/2022] Open
Abstract
Telomeres terminate with a 50-300 bases long single-stranded G-rich overhang, which can be misrecognized as a DNA damage repair site. Shelterin plays critical roles in maintaining and protecting telomere ends by regulating access of various physiological agents to telomeric DNA, but the underlying mechanism is not well understood. Here, we measure how shelterin affects the accessibility of long telomeric overhangs by monitoring transient binding events of a short complementary peptide nucleic acid (PNA) probe using FRET-PAINT in vitro. We observed that the POT1 subunit of shelterin reduces the accessibility of the PNA probe by ∼2.5-fold, indicating that POT1 effectively binds to and protects otherwise exposed telomeric sequences. In comparison, a four-component shelterin stabilizes POT1 binding to the overhang by tethering POT1 to the double-stranded telomeric DNA and reduces the accessibility of telomeric overhangs by ∼5-fold. This enhanced protection suggests shelterin restructures the junction between single and double-stranded telomere, which is otherwise the most accessible part of the telomeric overhang.
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Affiliation(s)
- Sajad Shiekh
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Amanda Jack
- Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
| | - Ayush Saurabh
- Center for Biological Physics, Department of Physics, Arizona State University, Tempe, AZ 85287, USA
| | - Golam Mustafa
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | | | - Prabesh Gyawali
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Mohammed Enamul Hoque
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA
| | - Steve Pressé
- Center for Biological Physics, Department of Physics, Arizona State University, Tempe, AZ 85287, USA
- School of Molecular Science, Arizona State University, Tempe, AZ 85287, USA
| | - Ahmet Yildiz
- Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
- Physics Department, University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Hamza Balci
- Department of Physics, Kent State University, Kent, OH 44242, USA
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9
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Cozzaglio M, Ceschi S, Groaz E, Sturlese M, Sissi C. G-quadruplexes formation within the promoter of TEAD4 oncogene and their interaction with Vimentin. Front Chem 2022; 10:1008075. [PMID: 36186582 PMCID: PMC9520404 DOI: 10.3389/fchem.2022.1008075] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Accepted: 08/24/2022] [Indexed: 11/13/2022] Open
Abstract
G-quadruplexes (G4s) are nucleic acid secondary structures detected within human chromosomes, that cluster at gene promoters and enhancers. This suggests that G4s may play specific roles in the regulation of gene expression. Within a distinct subgroup of G-rich domains, the formation of two or more adjacent G4 units (G4-repeats) is feasible. Recently it was shown that Vimentin, a protein highly expressed within mesenchymal cells, selectively recognizes these arrangements. Putative G4-repeats have been searched within the human gene proximal promoters by the bioinformatics tool QPARSE and they resulted to be enriched at genes related to epithelial-to-mesenchymal transition (EMT). This suggested that Vimentin binding at these sites might be relevant for the maintenance of the mesenchymal phenotype. Among all the identified sequences, in the present study we selected the one located within the promoter of the TEAD4 oncogene. TEAD4 codifies for a transcriptional enhancer factor, TEAD4, that actively promotes EMT, supporting, cell proliferation and migration. Moreover, in colorectal cancer cells TEAD4 directly enhances the expression of Vimentin. Thus, the possible interaction of Vimentin with TEAD4 promoter could highlight a positive feedback loop between these two factors, associated to important tumor metastasis related events. Here, we exploited spectroscopic and electrophoretic measurements under different conditions to address the folding behavior of the selected sequence. This allowed us to validate the folding of TEAD4 promoter into a G4-repeat able to interact with Vimentin.
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Affiliation(s)
- Marta Cozzaglio
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy
| | - Silvia Ceschi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy
| | - Elisabetta Groaz
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy
- KU Leuven, Rega Institute for Medical Research, KU Leuven, Medicinal Chemistry, Leuven, Belgium
| | - Mattia Sturlese
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy
| | - Claudia Sissi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy
- *Correspondence: Claudia Sissi,
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10
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Abstract
We present single-molecule experimental and computational modeling studies investigating the accessibility of human telomeric overhangs of physiologically relevant lengths. We studied 25 different overhangs that contain 4-28 repeats of GGGTTA (G-Tract) sequence and accommodate one to seven tandem G-quadruplex (GQ) structures. Using the FRET-PAINT method, we probed the distribution of accessible sites via a short imager strand, which is complementary to a G-Tract and transiently binds to available sites. We report accessibility patterns that periodically change with overhang length and interpret these patterns in terms of the underlying folding landscape and folding frustration. Overhangs that have [4n]G-Tracts, (12, 16, 20…) demonstrate the broadest accessibility patterns where the peptide nucleic acid probe accesses G-Tracts throughout the overhang. On the other hand, constructs with [4n+2]G-Tracts, (14, 18, 22…) have narrower patterns where the neighborhood of the junction between single- and double-stranded telomeres is most accessible. We interpret these results as the folding frustration being higher in [4n]G-Tract constructs compared to [4n+2]G-Tract constructs. We also developed a computational model that tests the consistency of different folding stabilities and cooperativities between neighboring GQs with the observed accessibility patterns. Our experimental and computational studies suggest the neighborhood of the junction between single- and double-stranded telomeres is least stable and most accessible, which is significant as this is a potential site where the connection between POT1/TPP1 (bound to single-stranded telomere) and other shelterin proteins (localized on double-stranded telomere) is established.
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11
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Thermally Induced Transitions of d(G4T4G3) Quadruplexes Can Be Described as Kinetically Driven Processes. Life (Basel) 2022; 12:life12060825. [PMID: 35743856 PMCID: PMC9225023 DOI: 10.3390/life12060825] [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: 04/06/2022] [Revised: 05/24/2022] [Accepted: 05/27/2022] [Indexed: 11/16/2022] Open
Abstract
DNA sequences that are rich in guanines and can form four-stranded structures are called G-quadruplexes. Due to the growing evidence that they may play an important role in several key biological processes, the G-quadruplexes have captured the interest of several researchers. G-quadruplexes may form in the presence of different metal cations as polymorphic structures formed in kinetically governed processes. Here we investigate a complex polymorphism of d(G4T4G3) quadruplexes at different K+ concentrations. We show that population size of different d(G4T4G3) quadruplex conformations can be manipulated by cooling rate and/or K+ concentration. We use a kinetic model to describe data obtained from DSC, CD and UV spectroscopy and PAGE experiments. Our model is able to describe the observed thermally induced conformational transitions of d(G4T4G3) quadruplexes at different K+ concentrations.
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12
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Rigo R, Groaz E, Sissi C. Polymorphic and Higher-Order G-Quadruplexes as Possible Transcription Regulators: Novel Perspectives for Future Anticancer Therapeutic Applications. Pharmaceuticals (Basel) 2022; 15:ph15030373. [PMID: 35337170 PMCID: PMC8950063 DOI: 10.3390/ph15030373] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 02/06/2023] Open
Abstract
In the past two decades, significant efforts have been put into designing small molecules to target selected genomic sites where DNA conformational rearrangements control gene expression. G-rich sequences at oncogene promoters are considered good points of intervention since, under specific environmental conditions, they can fold into non-canonical tetrahelical structures known as G-quadruplexes. However, emerging evidence points to a frequent lack of correlation between small molecule targeting of G-quadruplexes at gene promoters and the expression of the associated protein, which hampers pharmaceutical applications. The wide genomic localization of G-quadruplexes along with their highly polymorphic behavior may account for this scenario, suggesting the need for more focused drug design strategies. Here, we will summarize the G4 structural features that can be considered to fulfill this goal. In particular, by comparing a telomeric sequence with the well-characterized G-rich domain of the KIT promoter, we will address how multiple secondary structures might cooperate to control genome architecture at a higher level. If this holds true, the link between drug–DNA complex formation and the associated cellular effects will need to be revisited.
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Affiliation(s)
- Riccardo Rigo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Marzolo 5, 35131 Padova, Italy; (R.R.); (E.G.)
- CEITEC—Central European Institute of Technology, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic
| | - Elisabetta Groaz
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Marzolo 5, 35131 Padova, Italy; (R.R.); (E.G.)
- KU Leuven, Rega Institute for Medical Research, Medicinal Chemistry, Herestraat 49-Box 1041, 3000 Leuven, Belgium
| | - Claudia Sissi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Marzolo 5, 35131 Padova, Italy; (R.R.); (E.G.)
- Correspondence:
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Grün JT, Schwalbe H. Folding dynamics of polymorphic G-quadruplex structures. Biopolymers 2021; 113:e23477. [PMID: 34664713 DOI: 10.1002/bip.23477] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 09/30/2021] [Accepted: 09/30/2021] [Indexed: 12/14/2022]
Abstract
G-quadruplexes (G4), found in numerous places within the human genome, are involved in essential processes of cell regulation. Chromosomal DNA G4s are involved for example, in replication and transcription as first steps of gene expression. Hence, they influence a plethora of downstream processes. G4s possess an intricate structure that differs from canonical B-form DNA. Identical DNA G4 sequences can adopt multiple long-lived conformations, a phenomenon known as G4 polymorphism. A detailed understanding of the molecular mechanisms that drive G4 folding is essential to understand their ambivalent regulatory roles. Disentangling the inherent dynamic and polymorphic nature of G4 structures thus is key to unravel their biological functions and make them amenable as molecular targets in novel therapeutic approaches. We here review recent experimental approaches to monitor G4 folding and discuss structural aspects for possible folding pathways. Substantial progress in the understanding of G4 folding within the recent years now allows drawing comprehensive models of the complex folding energy landscape of G4s that we herein evaluate based on computational and experimental evidence.
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Affiliation(s)
- J Tassilo Grün
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Harald Schwalbe
- Institute for Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University, Frankfurt/M, Germany.,Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Frankfurt/M, Germany
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Choudhury A, Mohammad T, Samarth N, Hussain A, Rehman MT, Islam A, Alajmi MF, Singh S, Hassan MI. Structural genomics approach to investigate deleterious impact of nsSNPs in conserved telomere maintenance component 1. Sci Rep 2021; 11:10202. [PMID: 33986331 PMCID: PMC8119478 DOI: 10.1038/s41598-021-89450-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/14/2021] [Indexed: 02/07/2023] Open
Abstract
Conserved telomere maintenance component 1 (CTC1) is an important component of the CST (CTC1-STN1-TEN1) complex, involved in maintaining the stability of telomeric DNA. Several non-synonymous single-nucleotide polymorphisms (nsSNPs) in CTC1 have been reported to cause Coats plus syndrome and Dyskeratosis congenital diseases. Here, we have performed sequence and structure analyses of nsSNPs of CTC1 using state-of-the-art computational methods. The structure-based study focuses on the C-terminal OB-fold region of CTC1. There are 11 pathogenic mutations identified, and detailed structural analyses were performed. These mutations cause a significant disruption of noncovalent interactions, which may be a possible reason for CTC1 instability and consequent diseases. To see the impact of such mutations on the protein conformation, all-atom molecular dynamics (MD) simulations of CTC1-wild-type (WT) and two of the selected mutations, R806C and R806L for 200 ns, were carried out. A significant conformational change in the structure of the R806C mutant was observed. This study provides a valuable direction to understand the molecular basis of CTC1 dysfunction in disease progression, including Coats plus syndrome.
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Affiliation(s)
- Arunabh Choudhury
- Department of Computer Science, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India
| | - Taj Mohammad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India
| | - Nikhil Samarth
- National Centre for Cell Science, NCCS Complex, Ganeshkhind, SP Pune University, Campus, Pune, 411007, India
| | - Afzal Hussain
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Md Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India
| | - Mohamed F Alajmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Shailza Singh
- National Centre for Cell Science, NCCS Complex, Ganeshkhind, SP Pune University, Campus, Pune, 411007, India
| | - Md Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India.
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