1
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Ghahremani S, Kanwal A, Pettinato A, Ladha F, Legere N, Thakar K, Zhu Y, Tjong H, Wilderman A, Stump WT, Greenberg L, Greenberg MJ, Cotney J, Wei CL, Hinson JT. CRISPR Activation Reverses Haploinsufficiency and Functional Deficits Caused by TTN Truncation Variants. Circulation 2024; 149:1285-1297. [PMID: 38235591 PMCID: PMC11031707 DOI: 10.1161/circulationaha.123.063972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 12/13/2023] [Indexed: 01/19/2024]
Abstract
BACKGROUND TTN truncation variants (TTNtvs) are the most common genetic lesion identified in individuals with dilated cardiomyopathy, a disease with high morbidity and mortality rates. TTNtvs reduce normal TTN (titin) protein levels, produce truncated proteins, and impair sarcomere content and function. Therapeutics targeting TTNtvs have been elusive because of the immense size of TTN, the rarity of specific TTNtvs, and incomplete knowledge of TTNtv pathogenicity. METHODS We adapted CRISPR activation using dCas9-VPR to functionally interrogate TTNtv pathogenicity and develop a therapeutic in human cardiomyocytes and 3-dimensional cardiac microtissues engineered from induced pluripotent stem cell models harboring a dilated cardiomyopathy-associated TTNtv. We performed guide RNA screening with custom TTN reporter assays, agarose gel electrophoresis to quantify TTN protein levels and isoforms, and RNA sequencing to identify molecular consequences of TTN activation. Cardiomyocyte epigenetic assays were also used to nominate DNA regulatory elements to enable cardiomyocyte-specific TTN activation. RESULTS CRISPR activation of TTN using single guide RNAs targeting either the TTN promoter or regulatory elements in spatial proximity to the TTN promoter through 3-dimensional chromatin interactions rescued TTN protein deficits disturbed by TTNtvs. Increasing TTN protein levels normalized sarcomere content and contractile function despite increasing truncated TTN protein. In addition to TTN transcripts, CRISPR activation also increased levels of myofibril assembly-related and sarcomere-related transcripts. CONCLUSIONS TTN CRISPR activation rescued TTNtv-related functional deficits despite increasing truncated TTN levels, which provides evidence to support haploinsufficiency as a relevant genetic mechanism underlying heterozygous TTNtvs. CRISPR activation could be developed as a therapeutic to treat a large proportion of TTNtvs.
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Affiliation(s)
| | - Aditya Kanwal
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Anthony Pettinato
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Feria Ladha
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Nicholas Legere
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Ketan Thakar
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Yanfen Zhu
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Harianto Tjong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Andrea Wilderman
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - W. Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Lina Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Justin Cotney
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Chia-Lin Wei
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - J. Travis Hinson
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
- Cardiology Center, University of Connecticut Health Center, Farmington, CT 06030, USA
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2
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Murray GC, Bubier JA, Zinder OJ, Harris B, Clark J, Christopher MC, Hanley C, Tjong H, Li M, Ngan CY, Reinholdt L, Burgess RW, Tadenev ALD. An allelic series of spontaneous Rorb mutant mice exhibit a gait phenotype, changes in retina morphology and behavior, and gene expression signatures associated with the unfolded protein response. G3 (Bethesda) 2023; 13:jkad131. [PMID: 37300435 PMCID: PMC10411600 DOI: 10.1093/g3journal/jkad131] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 06/01/2023] [Accepted: 06/05/2023] [Indexed: 06/12/2023]
Abstract
The Retinoid-related orphan receptor beta (RORβ) gene encodes a developmental transcription factor and has 2 predominant isoforms created through alternative first exon usage; one specific to the retina and another present more broadly in the central nervous system, particularly regions involved in sensory processing. RORβ belongs to the nuclear receptor family and plays important roles in cell fate specification in the retina and cortical layer formation. In mice, loss of RORβ causes disorganized retina layers, postnatal degeneration, and production of immature cone photoreceptors. Hyperflexion or "high-stepping" of rear limbs caused by reduced presynaptic inhibition by Rorb-expressing inhibitory interneurons of the spinal cord is evident in RORβ-deficient mice. RORβ variants in patients are associated with susceptibility to various neurodevelopmental conditions, primarily generalized epilepsies, but including intellectual disability, bipolar, and autism spectrum disorders. The mechanisms by which RORβ variants confer susceptibility to these neurodevelopmental disorders are unknown but may involve aberrant neural circuit formation and hyperexcitability during development. Here we report an allelic series in 5 strains of spontaneous Rorb mutant mice with a high-stepping gait phenotype. We show retinal abnormalities in a subset of these mutants and demonstrate significant differences in various behavioral phenotypes related to cognition. Gene expression analyses in all 5 mutants reveal a shared over-representation of the unfolded protein response and pathways related to endoplasmic reticulum stress, suggesting a possible mechanism of susceptibility relevant to patients.
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Affiliation(s)
- George C Murray
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
- The Graduate School of Biomedical Science and Engineering, University of Maine, Orono, ME 04469, USA
| | | | | | | | - James Clark
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | | | | | - Harianto Tjong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Meihong Li
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Chew Yee Ngan
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | | | - Robert W Burgess
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
- The Graduate School of Biomedical Science and Engineering, University of Maine, Orono, ME 04469, USA
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3
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Zhu Y, Gujar AD, Wong CH, Tjong H, Ngan CY, Gong L, Chen YA, Kim H, Liu J, Li M, Mil-Homens A, Maurya R, Kuhlberg C, Sun F, Yi E, deCarvalho AC, Ruan Y, Verhaak RGW, Wei CL. Oncogenic extrachromosomal DNA functions as mobile enhancers to globally amplify chromosomal transcription. Cancer Cell 2021; 39:694-707.e7. [PMID: 33836152 PMCID: PMC8119378 DOI: 10.1016/j.ccell.2021.03.006] [Citation(s) in RCA: 94] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 11/05/2020] [Accepted: 03/12/2021] [Indexed: 12/13/2022]
Abstract
Extrachromosomal, circular DNA (ecDNA) is emerging as a prevalent yet less characterized oncogenic alteration in cancer genomes. We leverage ChIA-PET and ChIA-Drop chromatin interaction assays to characterize genome-wide ecDNA-mediated chromatin contacts that impact transcriptional programs in cancers. ecDNAs in glioblastoma patient-derived neurosphere and prostate cancer cell cultures are marked by widespread intra-ecDNA and genome-wide chromosomal interactions. ecDNA-chromatin contact foci are characterized by broad and high-level H3K27ac signals converging predominantly on chromosomal genes of increased expression levels. Prostate cancer cells harboring synthetic ecDNA circles composed of characterized enhancers result in the genome-wide activation of chromosomal gene transcription. Deciphering the chromosomal targets of ecDNAs at single-molecule resolution reveals an association with actively expressed oncogenes spatially clustered within ecDNA-directed interaction networks. Our results suggest that ecDNA can function as mobile transcriptional enhancers to promote tumor progression and manifest a potential synthetic aneuploidy mechanism of transcription control in cancer.
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Affiliation(s)
- Yanfen Zhu
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Amit D Gujar
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Chee-Hong Wong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Harianto Tjong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Chew Yee Ngan
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Liang Gong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Yi-An Chen
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Hoon Kim
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Jihe Liu
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Meihong Li
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Adam Mil-Homens
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Rahul Maurya
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Chris Kuhlberg
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Fanyue Sun
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Eunhee Yi
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Ana C deCarvalho
- Department of Neurosurgery, Henry Ford Hospital, Detroit, MI 48202, USA
| | - Yijun Ruan
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA
| | - Roel G W Verhaak
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA.
| | - Chia-Lin Wei
- The Jackson Laboratory for Genomic Medicine, Farmington, CT 06032, USA.
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4
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Lee B, Wang J, Cai L, Kim M, Namburi S, Tjong H, Feng Y, Wang P, Tang Z, Abbas A, Wei CL, Ruan Y, Li S. ChIA-PIPE: A fully automated pipeline for comprehensive ChIA-PET data analysis and visualization. Sci Adv 2020; 6:eaay2078. [PMID: 32832596 PMCID: PMC7439456 DOI: 10.1126/sciadv.aay2078] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 05/28/2020] [Indexed: 06/11/2023]
Abstract
ChIA-PET (chromatin interaction analysis with paired-end tags) enables genome-wide discovery of chromatin interactions involving specific protein factors, with base pair resolution. Interpretation of ChIA-PET data requires a robust analytic pipeline. Here, we introduce ChIA-PIPE, a fully automated pipeline for ChIA-PET data processing, quality assessment, visualization, and analysis. ChIA-PIPE performs linker filtering, read mapping, peak calling, and loop calling and automates quality control assessment for each dataset. To enable visualization, ChIA-PIPE generates input files for two-dimensional contact map viewing with Juicebox and HiGlass and provides a new dockerized visualization tool for high-resolution, browser-based exploration of peaks and loops. To enable structural interpretation, ChIA-PIPE calls chromatin contact domains, resolves allele-specific peaks and loops, and annotates enhancer-promoter loops. ChIA-PIPE also supports the analysis of other related chromatin-mapping data types.
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Affiliation(s)
- Byoungkoo Lee
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Jiahui Wang
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Liuyang Cai
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Minji Kim
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Sandeep Namburi
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Harianto Tjong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Yuliang Feng
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Ping Wang
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Zhonghui Tang
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Ahmed Abbas
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Chia-Lin Wei
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
- The Jackson Laboratory Cancer Center, Bar Harbor, ME, USA
| | - Yijun Ruan
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
- The Jackson Laboratory Cancer Center, Bar Harbor, ME, USA
- Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, CT, USA
| | - Sheng Li
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
- The Jackson Laboratory Cancer Center, Bar Harbor, ME, USA
- Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, CT, USA
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT, USA
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5
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Bertolini JA, Favaro R, Zhu Y, Pagin M, Ngan CY, Wong CH, Tjong H, Vermunt MW, Martynoga B, Barone C, Mariani J, Cardozo MJ, Tabanera N, Zambelli F, Mercurio S, Ottolenghi S, Robson P, Creyghton MP, Bovolenta P, Pavesi G, Guillemot F, Nicolis SK, Wei CL. Mapping the Global Chromatin Connectivity Network for Sox2 Function in Neural Stem Cell Maintenance. Cell Stem Cell 2020; 24:462-476.e6. [PMID: 30849367 PMCID: PMC6506828 DOI: 10.1016/j.stem.2019.02.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 07/16/2018] [Accepted: 02/06/2019] [Indexed: 11/29/2022]
Abstract
The SOX2 transcription factor is critical for neural stem cell (NSC) maintenance and brain development. Through chromatin immunoprecipitation (ChIP) and chromatin interaction analysis (ChIA-PET), we determined genome-wide SOX2-bound regions and Pol II-mediated long-range chromatin interactions in brain-derived NSCs. SOX2-bound DNA was highly enriched in distal chromatin regions interacting with promoters and carrying epigenetic enhancer marks. Sox2 deletion caused widespread reduction of Pol II-mediated long-range interactions and decreased gene expression. Genes showing reduced expression in Sox2-deleted cells were significantly enriched in interactions between promoters and SOX2-bound distal enhancers. Expression of one such gene, Suppressor of Cytokine Signaling 3 (Socs3), rescued the self-renewal defect of Sox2-ablated NSCs. Our work identifies SOX2 as a major regulator of gene expression through connections to the enhancer network in NSCs. Through the definition of such a connectivity network, our study shows the way to the identification of genes and enhancers involved in NSC maintenance and neurodevelopmental disorders. Sox2-bound enhancers are enriched within long-range interactions in neural stem cells SOX2 loss decreases chromatin interactivity genome-wide Sox2-bound enhancers from interactions activate reporter genes in zebrafish forebrain Socs3, a gene downregulated in Sox2 mutant NSCs, rescues their self-renewal
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Affiliation(s)
- Jessica A Bertolini
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
| | - Rebecca Favaro
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
| | - Yanfen Zhu
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Miriam Pagin
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
| | - Chew Yee Ngan
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Chee Hong Wong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Harianto Tjong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Marit W Vermunt
- Hubrecht Institute-KNAW and University Medical Center Utrecht 3584CT, Utrecht, the Netherlands
| | - Ben Martynoga
- The Francis Crick Institute, Midland Road, London NW 1AT, UK
| | - Cristiana Barone
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
| | - Jessica Mariani
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
| | - Marcos Julián Cardozo
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid and Ciber de Enfermedades Raras (CIBERER), ISCIII Madrid, Spain
| | - Noemi Tabanera
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid and Ciber de Enfermedades Raras (CIBERER), ISCIII Madrid, Spain
| | - Federico Zambelli
- Department of Biosciences, University of Milano, 20133 Milano, Italy
| | - Sara Mercurio
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
| | - Sergio Ottolenghi
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
| | - Paul Robson
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA; Stem Cell and Regenerative Biology, Genome Institute of Singapore, Singapore
| | - Menno P Creyghton
- Hubrecht Institute-KNAW and University Medical Center Utrecht 3584CT, Utrecht, the Netherlands
| | - Paola Bovolenta
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid and Ciber de Enfermedades Raras (CIBERER), ISCIII Madrid, Spain
| | - Giulio Pavesi
- Department of Biosciences, University of Milano, 20133 Milano, Italy
| | | | - Silvia K Nicolis
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy.
| | - Chia-Lin Wei
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA.
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6
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Gong L, Wong CH, Cheng WC, Tjong H, Menghi F, Ngan CY, Liu ET, Wei CL. Picky comprehensively detects high-resolution structural variants in nanopore long reads. Nat Methods 2018; 15:455-460. [PMID: 29713081 PMCID: PMC5990454 DOI: 10.1038/s41592-018-0002-6] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 03/14/2018] [Indexed: 12/11/2022]
Abstract
Acquired genomic structural variants (SVs) are major hallmarks of cancer genomes, but they are challenging to reconstruct from short-read sequencing data. Here we exploited the long reads of the nanopore platform using our customized pipeline, Picky ( https://github.com/TheJacksonLaboratory/Picky ), to reveal SVs of diverse architecture in a breast cancer model. We identified the full spectrum of SVs with superior specificity and sensitivity relative to short-read analyses, and uncovered repetitive DNA as the major source of variation. Examination of genome-wide breakpoints at nucleotide resolution uncovered micro-insertions as the common structural features associated with SVs. Breakpoint density across the genome is associated with the propensity for interchromosomal connectivity and was found to be enriched in promoters and transcribed regions of the genome. Furthermore, we observed an over-representation of reciprocal translocations from chromosomal double-crossovers through phased SVs. We demonstrate that Picky analysis is an effective tool for comprehensive detection of SVs in cancer genomes from long-read data.
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Affiliation(s)
- Liang Gong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Chee-Hong Wong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | | | - Harianto Tjong
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Francesca Menghi
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Chew Yee Ngan
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Edison T Liu
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Chia-Lin Wei
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA.
- China Medical University, Taichung, Taiwan.
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7
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Caridi CP, Delabaere L, Tjong H, Hopp H, Das D, Alber F, Chiolo I. Quantitative Methods to Investigate the 4D Dynamics of Heterochromatic Repair Sites in Drosophila Cells. Methods Enzymol 2018. [PMID: 29523239 DOI: 10.1016/bs.mie.2017.11.033] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Heterochromatin is mostly composed of long stretches of repeated DNA sequences prone to ectopic recombination during double-strand break (DSB) repair. In Drosophila, "safe" homologous recombination (HR) repair of heterochromatic DSBs relies on a striking relocalization of repair sites to the nuclear periphery. Central to understanding heterochromatin repair is the ability to investigate the 4D dynamics (movement in space and time) of repair sites. A specific challenge of these studies is preventing phototoxicity and photobleaching effects while imaging the sample over long periods of time, and with sufficient time points and Z-stacks to track repair foci over time. Here we describe an optimized approach for high-resolution live imaging of heterochromatic DSBs in Drosophila cells, with a specific emphasis on the fluorescent markers and imaging setup used to capture the motion of repair foci over long-time periods. We detail approaches that minimize photobleaching and phototoxicity with a DeltaVision widefield deconvolution microscope, and image processing techniques for signal recovery postimaging using SoftWorX and Imaris software. We present a method to derive mean square displacement curves revealing some of the biophysical properties of the motion. Finally, we describe a method in R to identify tracts of directed motions (DMs) in mixed trajectories. These approaches enable a deeper understanding of the mechanisms of heterochromatin dynamics and genome stability in the three-dimensional context of the nucleus and have broad applicability in the field of nuclear dynamics.
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Affiliation(s)
| | | | - Harianto Tjong
- University of Southern California, Los Angeles, CA, United States
| | - Hannah Hopp
- University of Southern California, Los Angeles, CA, United States
| | - Devika Das
- University of Southern California, Los Angeles, CA, United States
| | - Frank Alber
- University of Southern California, Los Angeles, CA, United States
| | - Irene Chiolo
- University of Southern California, Los Angeles, CA, United States.
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8
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Li Q, Tjong H, Li X, Gong K, Zhou XJ, Chiolo I, Alber F. The three-dimensional genome organization of Drosophila melanogaster through data integration. Genome Biol 2017; 18:145. [PMID: 28760140 PMCID: PMC5576134 DOI: 10.1186/s13059-017-1264-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Accepted: 06/26/2017] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Genome structures are dynamic and non-randomly organized in the nucleus of higher eukaryotes. To maximize the accuracy and coverage of three-dimensional genome structural models, it is important to integrate all available sources of experimental information about a genome's organization. It remains a major challenge to integrate such data from various complementary experimental methods. Here, we present an approach for data integration to determine a population of complete three-dimensional genome structures that are statistically consistent with data from both genome-wide chromosome conformation capture (Hi-C) and lamina-DamID experiments. RESULTS Our structures resolve the genome at the resolution of topological domains, and reproduce simultaneously both sets of experimental data. Importantly, this data deconvolution framework allows for structural heterogeneity between cells, and hence accounts for the expected plasticity of genome structures. As a case study we choose Drosophila melanogaster embryonic cells, for which both data types are available. Our three-dimensional genome structures have strong predictive power for structural features not directly visible in the initial data sets, and reproduce experimental hallmarks of the D. melanogaster genome organization from independent and our own imaging experiments. Also they reveal a number of new insights about genome organization and its functional relevance, including the preferred locations of heterochromatic satellites of different chromosomes, and observations about homologous pairing that cannot be directly observed in the original Hi-C or lamina-DamID data. CONCLUSIONS Our approach allows systematic integration of Hi-C and lamina-DamID data for complete three-dimensional genome structure calculation, while also explicitly considering genome structural variability.
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Affiliation(s)
- Qingjiao Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Harianto Tjong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Xiao Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Ke Gong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Xianghong Jasmine Zhou
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, USA
| | - Irene Chiolo
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA.
| | - Frank Alber
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA.
- Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90089, USA.
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9
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Batra J, Tjong H, Zhou HX. Electrostatic effects on the folding stability of FKBP12. Protein Eng Des Sel 2016; 29:301-308. [PMID: 27381026 PMCID: PMC4955870 DOI: 10.1093/protein/gzw014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 03/28/2016] [Accepted: 04/15/2016] [Indexed: 01/17/2023] Open
Abstract
The roles of electrostatic interactions in protein folding stability have been a matter of debate, largely due to the complexity in the theoretical treatment of these interactions. We have developed computational methods for calculating electrostatic effects on protein folding stability. To rigorously test and further refine these methods, here we carried out experimental studies into electrostatic effects on the folding stability of the human 12-kD FK506 binding protein (FKBP12). This protein has a close homologue, FKBP12.6, with amino acid substitutions in only 18 of their 107 residues. Of the 18 substitutions, 8 involve charged residues. Upon mutating FKBP12 residues at these 8 positions individually into the counterparts in FKBP12.6, the unfolding free energy (ΔGu) of FKBP12 changed by -0.3 to 0.7 kcal/mol. Accumulating stabilizing substitutions resulted in a mutant with a 0.9 kcal/mol increase in stability. Additional charge mutations were grafted from a thermophilic homologue, MtFKBP17, which aligns to FKBP12 with 31% sequence identity over 89 positions. Eleven such charge mutations were studied, with ΔΔGu varying from -2.9 to 0.1 kcal/mol. The predicted electrostatic effects by our computational methods with refinements herein had a root-mean-square deviation of 0.9 kcal/mol from the experimental ΔΔGu values on 16 single mutations of FKBP12. The difference in ΔΔGu between mutations grafted from FKBP12.6 and those from MtFKBP17 suggests that more distant homologues are less able to provide guidance for enhancing folding stability.
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Affiliation(s)
- Jyotica Batra
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
- Present address: Department of Chemistry and Physics, Bellarmine University, 2001 Newburg Road, Louisville, KY40205, USA
| | - Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
- Present address: Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
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10
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Dai C, Li W, Tjong H, Hao S, Zhou Y, Li Q, Chen L, Zhu B, Alber F, Jasmine Zhou X. Mining 3D genome structure populations identifies major factors governing the stability of regulatory communities. Nat Commun 2016; 7:11549. [PMID: 27240697 PMCID: PMC4895025 DOI: 10.1038/ncomms11549] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 04/08/2016] [Indexed: 11/25/2022] Open
Abstract
Three-dimensional (3D) genome structures vary from cell to cell even in an isogenic sample. Unlike protein structures, genome structures are highly plastic, posing a significant challenge for structure-function mapping. Here we report an approach to comprehensively identify 3D chromatin clusters that each occurs frequently across a population of genome structures, either deconvoluted from ensemble-averaged Hi-C data or from a collection of single-cell Hi-C data. Applying our method to a population of genome structures (at the macrodomain resolution) of lymphoblastoid cells, we identify an atlas of stable inter-chromosomal chromatin clusters. A large number of these clusters are enriched in binding of specific regulatory factors and are therefore defined as ‘Regulatory Communities.' We reveal two major factors, centromere clustering and transcription factor binding, which significantly stabilize such communities. Finally, we show that the regulatory communities differ substantially from cell to cell, indicating that expression variability could be impacted by genome structures. 3D genome structures are plastic and vary from cell to cell even in an isogenic sample. Here, the authors present an approach to identify frequent 3D chromatin clusters across a population of genome structures, either deconvoluted from ensemble-averaged Hi-C data or from a collection of single-cell Hi-C data.
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Affiliation(s)
- Chao Dai
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Wenyuan Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Harianto Tjong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Shengli Hao
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Yonggang Zhou
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Qingjiao Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Lin Chen
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Bing Zhu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Frank Alber
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
| | - Xianghong Jasmine Zhou
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA
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11
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Dultz E, Tjong H, Weider E, Herzog M, Young B, Brune C, Müllner D, Loewen C, Alber F, Weis K. Global reorganization of budding yeast chromosome conformation in different physiological conditions. J Cell Biol 2016; 212:321-34. [PMID: 26811423 PMCID: PMC4748577 DOI: 10.1083/jcb.201507069] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 01/05/2016] [Indexed: 12/31/2022] Open
Abstract
The organization of the genome is nonrandom and important for correct function. Specifically, the nuclear envelope plays a critical role in gene regulation. It generally constitutes a repressive environment, but several genes, including the GAL locus in budding yeast, are recruited to the nuclear periphery on activation. Here, we combine imaging and computational modeling to ask how the association of a single gene locus with the nuclear envelope influences the surrounding chromosome architecture. Systematic analysis of an entire yeast chromosome establishes that peripheral recruitment of the GAL locus is part of a large-scale rearrangement that shifts many chromosomal regions closer to the nuclear envelope. This process is likely caused by the presence of several independent anchoring points. To identify novel factors required for peripheral anchoring, we performed a genome-wide screen and demonstrated that the histone acetyltransferase SAGA and the activity of histone deacetylases are needed for this extensive gene recruitment to the nuclear periphery.
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Affiliation(s)
- Elisa Dultz
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zurich, 8093 Zurich, Switzerland
| | - Harianto Tjong
- Department of Biological Sciences, Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089
| | - Elodie Weider
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Mareike Herzog
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Barry Young
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T1Z3, Canada
| | - Christiane Brune
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Daniel Müllner
- Department of Mathematics, Stanford University, Stanford, CA 94305
| | - Christopher Loewen
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T1Z3, Canada
| | - Frank Alber
- Department of Biological Sciences, Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089
| | - Karsten Weis
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule Zurich, 8093 Zurich, Switzerland
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12
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Shin H, Shi Y, Dai C, Tjong H, Gong K, Alber F, Zhou XJ. TopDom: an efficient and deterministic method for identifying topological domains in genomes. Nucleic Acids Res 2015; 44:e70. [PMID: 26704975 PMCID: PMC4838359 DOI: 10.1093/nar/gkv1505] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 12/09/2015] [Indexed: 11/14/2022] Open
Abstract
Genome-wide proximity ligation assays allow the identification of chromatin contacts at unprecedented resolution. Several studies reveal that mammalian chromosomes are composed of topological domains (TDs) in sub-mega base resolution, which appear to be conserved across cell types and to some extent even between organisms. Identifying topological domains is now an important step toward understanding the structure and functions of spatial genome organization. However, current methods for TD identification demand extensive computational resources, require careful tuning and/or encounter inconsistencies in results. In this work, we propose an efficient and deterministic method, TopDom, to identify TDs, along with a set of statistical methods for evaluating their quality. TopDom is much more efficient than existing methods and depends on just one intuitive parameter, a window size, for which we provide easy-to-implement optimization guidelines. TopDom also identifies more and higher quality TDs than the popular directional index algorithm. The TDs identified by TopDom provide strong support for the cross-tissue TD conservation. Finally, our analysis reveals that the locations of housekeeping genes are closely associated with cross-tissue conserved TDs. The software package and source codes of TopDom are available at http://zhoulab.usc.edu/TopDom/.
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Affiliation(s)
- Hanjun Shin
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90033, USA
| | - Yi Shi
- Key Laboratory of Systems Biomedicine, Ministry of Education, Shanghai Center for Systems Biomedicine, Shanghai Jiaotong University, Shanghai 200240, China
| | - Chao Dai
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90033, USA
| | - Harianto Tjong
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90033, USA
| | - Ke Gong
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90033, USA
| | - Frank Alber
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90033, USA
| | - Xianghong Jasmine Zhou
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90033, USA
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13
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Abstract
We studied the 3D structural organization of the fission yeast genome, which emerges from the tethering of heterochromatic regions in otherwise randomly configured chromosomes represented as flexible polymer chains in an nuclear environment. This model is sufficient to explain in a statistical manner many experimentally determined distinctive features of the fission yeast genome, including chromatin interaction patterns from Hi-C experiments and the co-locations of functionally related and co-expressed genes, such as genes expressed by Pol-III. Our findings demonstrate that some previously described structure-function correlations can be explained as a consequence of random chromatin collisions driven by a few geometric constraints (mainly due to centromere-SPB and telomere-NE tethering) combined with the specific gene locations in the chromosome sequence. We also performed a comparative analysis between the fission and budding yeast genome structures, for which we previously detected a similar organizing principle. However, due to the different chromosome sizes and numbers, substantial differences are observed in the 3D structural genome organization between the two species, most notably in the nuclear locations of orthologous genes, and the extent of nuclear territories for genes and chromosomes. However, despite those differences, remarkably, functional similarities are maintained, which is evident when comparing spatial clustering of functionally related genes in both yeasts. Functionally related genes show a similar spatial clustering behavior in both yeasts, even though their nuclear locations are largely different between the yeast species.
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Affiliation(s)
- Ke Gong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089, United States of America
| | - Harianto Tjong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089, United States of America
| | - Xianghong Jasmine Zhou
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089, United States of America
- * E-mail: (FA); (XJZ)
| | - Frank Alber
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA 90089, United States of America
- * E-mail: (FA); (XJZ)
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14
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Abstract
In this paper we show that tethering of heterochromatic regions to nuclear landmarks and random encounters of chromosomes in the confined nuclear volume are sufficient to explain the higher-order organization of the budding yeast genome. We have quantitatively characterized the contact patterns and nuclear territories that emerge when chromosomes are allowed to behave as constrained but otherwise randomly configured flexible polymer chains in the nucleus. Remarkably, this constrained random encounter model explains in a statistical manner the experimental hallmarks of the S. cerevisiae genome organization, including (1) the folding patterns of individual chromosomes; (2) the highly enriched interactions between specific chromatin regions and chromosomes; (3) the emergence, shape, and position of gene territories; (4) the mean distances between pairs of telomeres; and (5) even the co-location of functionally related gene loci, including early replication start sites and tRNA genes. Therefore, most aspects of the yeast genome organization can be explained without calling on biochemically mediated chromatin interactions. Such interactions may modulate the pre-existing propensity for co-localization but seem not to be the cause for the observed higher-order organization. The fact that geometrical constraints alone yield a highly organized genome structure, on which different functional elements are specifically distributed, has strong implications for the folding principles of the genome and the evolution of its function.
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Affiliation(s)
- Harianto Tjong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
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15
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Beck M, Topf M, Frazier Z, Tjong H, Xu M, Zhang S, Alber F. Exploring the spatial and temporal organization of a cell's proteome. J Struct Biol 2011; 173:483-96. [PMID: 21094684 PMCID: PMC3784337 DOI: 10.1016/j.jsb.2010.11.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2010] [Revised: 11/05/2010] [Accepted: 11/08/2010] [Indexed: 10/18/2022]
Abstract
To increase our current understanding of cellular processes, such as cell signaling and division, knowledge is needed about the spatial and temporal organization of the proteome at different organizational levels. These levels cover a wide range of length and time scales: from the atomic structures of macromolecules for inferring their molecular function, to the quantitative description of their abundance, and spatial distribution in the cell. Emerging new experimental technologies are greatly increasing the availability of such spatial information on the molecular organization in living cells. This review addresses three fields that have significantly contributed to our understanding of the proteome's spatial and temporal organization: first, methods for the structure determination of individual macromolecular assemblies, specifically the fitting of atomic structures into density maps generated from electron microscopy techniques; second, research that visualizes the spatial distributions of these complexes within the cellular context using cryo electron tomography techniques combined with computational image processing; and third, methods for the spatial modeling of the dynamic organization of the proteome, specifically those methods for simulating reaction and diffusion of proteins and complexes in crowded intracellular fluids. The long-term goal is to integrate the varied data about a proteome's organization into a spatially explicit, predictive model of cellular processes.
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Affiliation(s)
- Martin Beck
- European Molecular Biology Laboratory, Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Maya Topf
- Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck College, University of London, London, UK
| | - Zachary Frazier
- Program in Molecular and Computational Biology, University of Southern California, 1050 Childs Way, RRI 413E, Los Angeles, CA 90068, USA
| | - Harianto Tjong
- Program in Molecular and Computational Biology, University of Southern California, 1050 Childs Way, RRI 413E, Los Angeles, CA 90068, USA
| | - Min Xu
- Program in Molecular and Computational Biology, University of Southern California, 1050 Childs Way, RRI 413E, Los Angeles, CA 90068, USA
| | - Shihua Zhang
- Program in Molecular and Computational Biology, University of Southern California, 1050 Childs Way, RRI 413E, Los Angeles, CA 90068, USA
| | - Frank Alber
- Program in Molecular and Computational Biology, University of Southern California, 1050 Childs Way, RRI 413E, Los Angeles, CA 90068, USA
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16
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Tjong H, Zhou HX. The folding transition-state ensemble of a four-helix bundle protein: helix propensity as a determinant and macromolecular crowding as a probe. Biophys J 2010; 98:2273-80. [PMID: 20483336 DOI: 10.1016/j.bpj.2010.01.052] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Revised: 12/21/2009] [Accepted: 01/05/2010] [Indexed: 10/19/2022] Open
Abstract
The four-helix bundle protein Rd-apocyt b(562), a redesigned stable variant of apocytochrome b(562), exhibits two-state folding kinetics. Its transition-state ensemble has been characterized by Phi-value analysis. To elucidate the molecular basis of the transition-state ensemble, we have carried out high-temperature molecular dynamics simulations of the unfolding process. In six parallel simulations, unfolding started with the melting of helix I and the C-terminal half of helix IV, and followed by helix III, the N-terminal half of helix IV and helix II. This ordered melting of the helices is consistent with the conclusion from native-state hydrogen exchange, and can be rationalized by differences in intrinsic helix propensity. Guided by experimental Phi-values, a putative transition-state ensemble was extracted from the simulations. The residue helical probabilities of this transition-state ensemble show good correlation with the Phi-values. To further validate the putative transition-state ensemble, the effect of macromolecular crowding on the relative stability between the unfolded ensemble and the transition-state ensemble was calculated. The resulting effect of crowding on the folding kinetics agrees well with experimental observations. This study shows that molecular dynamics simulations combined with calculation of crowding effects provide an avenue for characterize the transition-state ensemble in atomic details.
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Affiliation(s)
- Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, USA
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17
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Maniccia AW, Yang W, Johnson JA, Li S, Tjong H, Zhou HX, Shaket LA, Yang JJ. Inverse tuning of metal binding affinity and protein stability by altering charged coordination residues in designed calcium binding proteins. PMC Biophys 2009; 2:11. [PMID: 20025729 PMCID: PMC2816670 DOI: 10.1186/1757-5036-2-11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Accepted: 12/21/2009] [Indexed: 11/10/2022]
Abstract
Ca(2+ )binding proteins are essential for regulating the role of Ca(2+ )in cell signaling and maintaining Ca(2+ )homeostasis. Negatively charged residues such as Asp and Glu are often found in Ca(2+ )binding proteins and are known to influence Ca(2+ )binding affinity and protein stability. In this paper, we report a systematic investigation of the role of local charge number and type of coordination residues in Ca(2+ )binding and protein stability using de novo designed Ca(2+ )binding proteins. The approach of de novo design was chosen to avoid the complications of cooperative binding and Ca(2+)-induced conformational change associated with natural proteins. We show that when the number of negatively charged coordination residues increased from 2 to 5 in a relatively restricted Ca(2+)-binding site, Ca(2+ )binding affinities increased by more than 3 orders of magnitude and metal selectivity for trivalent Ln(3+ )over divalent Ca(2+ )increased by more than 100-fold. Additionally, the thermal transition temperatures of the apo forms of the designed proteins decreased due to charge repulsion at the Ca(2+ )binding pocket. The thermal stability of the proteins was regained upon Ca(2+ )and Ln(3+ )binding to the designed Ca(2+ )binding pocket. We therefore observe a striking tradeoff between Ca(2+)/Ln(3+ )affinity and protein stability when the net charge of the coordination residues is varied. Our study has strong implications for understanding and predicting Ca(2+)-conferred thermal stabilization of natural Ca(2+ )binding proteins as well as for designing novel metalloproteins with tunable Ca(2+ )and Ln(3+ )binding affinity and selectivity.PACS codes: 05.10.-a.
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Affiliation(s)
- Anna Wilkins Maniccia
- Department of Chemistry, Center for Drug Design and Biotechnology, Georgia State University, Atlanta, GA 30303, USA
| | - Wei Yang
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Road 5625, Changchun, Jilin 130022, PR China
| | - Julian A Johnson
- Department of Chemistry, Center for Drug Design and Biotechnology, Georgia State University, Atlanta, GA 30303, USA
| | - Shunyi Li
- Department of Chemistry, Center for Drug Design and Biotechnology, Georgia State University, Atlanta, GA 30303, USA
| | - Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics and School of Computational Science, Florida State University, Tallahassee, Florida 32306, USA
| | - Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics and School of Computational Science, Florida State University, Tallahassee, Florida 32306, USA
| | - Lev A Shaket
- Department of Chemistry, Center for Drug Design and Biotechnology, Georgia State University, Atlanta, GA 30303, USA
| | - Jenny J Yang
- Department of Chemistry, Center for Drug Design and Biotechnology, Georgia State University, Atlanta, GA 30303, USA
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18
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Tjong H, Batra J, Zhou HX. Computational Model to Predict Folding Stability of FKBP. Biophys J 2009. [DOI: 10.1016/j.bpj.2008.12.1497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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19
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Li S, Yang W, Maniccia AW, Barrow D, Tjong H, Zhou HX, Yang JJ. Rational design of a conformation-switchable Ca2+- and Tb3+-binding protein without the use of multiple coupled metal-binding sites. FEBS J 2008; 275:5048-61. [PMID: 18785925 DOI: 10.1111/j.1742-4658.2008.06638.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Ca2+, as a messenger of signal transduction, regulates numerous target molecules via Ca2+-induced conformational changes. Investigation into the determinants for Ca2+-induced conformational change is often impeded by cooperativity between multiple metal-binding sites or protein oligomerization in naturally occurring proteins. To dissect the relative contributions of key determinants for Ca2+-dependent conformational changes, we report the design of a single-site Ca2+-binding protein (CD2.trigger) created by altering charged residues at an electrostatically sensitive location on the surface of the host protein rat Cluster of Differentiation 2 (CD2).CD2.trigger binds to Tb3+ and Ca2+ with dissociation constants of 0.3 +/- 0.1 and 90 +/- 25 microM, respectively. This protein is largely unfolded in the absence of metal ions at physiological pH, but Tb3+ or Ca2+ binding results in folding of the native-like conformation. Neutralization of the charged coordination residues, either by mutation or protonation, similarly induces folding of the protein. The control of a major conformational change by a single Ca2+ ion, achieved on a protein designed without reliance on sequence similarity to known Ca2+-dependent proteins and coupled metal-binding sites, represents an important step in the design of trigger proteins.
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Affiliation(s)
- Shunyi Li
- Department of Chemistry, Center of Drug Design and Biotechnology, Georgia State University, Atlanta, GA, USA
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20
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Tjong H, Zhou HX. Accurate Calculations of Binding, Folding, and Transfer Free Energies by a Scaled Generalized Born Method. J Chem Theory Comput 2008; 4:1733-1744. [PMID: 23468599 DOI: 10.1021/ct8001656] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The Poisson-Boltzmann (PB) equation is widely used for modeling solvation effects. The computational cost of PB has restricted its applications largely to single-conformation calculations. The generalized Born (GB) model provides an approximation at substantially reduced cost. Currently the best GB methods reproduce PB results for electrostatic solvation energies with errors at ~5 kcal/mol. When two proteins form a complex, the net electrostatic contributions to the binding free energy are typically of the order of 5 to 10 kcal/mol. Similarly, the net contributions of individual residues to protein folding free energy are < 5 kcal/mol. Clearly in these applications the accuracy of current GB methods is insufficient. Here we present a simple scaling scheme that allows our GB method, GBr6, to reproduce PB results for binding, folding, and transfer free energies with high accuracy. From an ensemble of conformations sampled from molecular dynamics simulations, five were judiciously selected for PB calculations. These PB results were used for scaling GBr6. Tests on the binding free energies of the barnase-barstar, GTPase-WASp, and U1A-U1hpII complexes and on the folding free energy of FKBP show that the effects of point mutations calculated by scaled GBr6 are accurate to within 0.3 kcal/mol of PB results. Similar accuracy was also achieved for the free energies of transfer for ribonuclease Sa and insulin from the crystalline phase to the solution phase at various pH's. This method makes it possible to thoroughly sample the transient-complex ensemble in predicting protein binding rate constants and to incorporate conformational sampling in electrostatic modeling (such as done in the MM-GBSA approach) without loss of accuracy.
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Affiliation(s)
- Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics and School of Computational Science, Florida State University, Tallahassee, FL 32306
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21
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Abstract
In applying the Poisson-Boltzmann (PB) equation for calculating the electrostatic free energies of solute molecules, an open question is how to specify the boundary between the low-dielectric solute and the high-dielectric solvent. Two common specifications of the dielectric boundary, as the molecular surface (MS) or the van der Waals (vdW) surface of the solute, give very different results for the electrostatic free energy of the solute. With the same atomic radii, the solute is more solvent-exposed in the vdW specification. One way to resolve the difference is to use different sets of atomic radii for the two surfaces. The radii for the vdW surface would be larger in order to compensate for the higher solvent exposure. Here we show that radius re-parameterization required for bringing MS-based and vdW-based PB results to agreement is solute-size dependent. The difference in atomic radii for individual amino acids as solutes is only 2-5% but increases to over 20% for proteins with ~200 residues. Therefore two sets of radii that yield identical MS-based and vdW-based PB results for small solutes will give very different PB results for large solutes. This finding raises issues about two common practices. The first is the use of atomic radii, which are parameterized against either experimental solvation data or data obtained from explicit-solvent simulations on small compounds, for PB calculations on proteins. The second is the parameterization of vdW-based generalized Born models against MS-based PB results.
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Affiliation(s)
- Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics and School of Computational Science Florida State University Tallahassee, FL 32306
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22
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Zhou HX, Qin S, Tjong H. Modeling Protein–Protein and Protein–Nucleic Acid Interactions: Structure, Thermodynamics, and Kinetics. Annual Reports in Computational Chemistry 2008. [DOI: 10.1016/s1574-1400(08)00004-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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23
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Tjong H, Zhou HX. GBr6NL: a generalized Born method for accurately reproducing solvation energy of the nonlinear Poisson-Boltzmann equation. J Chem Phys 2007; 126:195102. [PMID: 17523838 DOI: 10.1063/1.2735322] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The nonlinear Poisson-Boltzmann (NLPB) equation can provide accurate modeling of electrostatic effects for nucleic acids and highly charged proteins. Generalized Born methods have been developed to mimic the linearized Poisson-Boltzmann (LPB) equation at substantially reduced cost. The computer time for solving the NLPB equation is approximately fivefold longer than for the LPB equation, thus presenting an even greater obstacle. Here we present the first generalized Born method, GBr(6)NL, for mimicking the NLPB equation. GBr(6)NL is adapted from GBr(6), a generalized Born method recently developed to reproduce the solvation energy of the LPB equation [Tjong and Zhou, J. Phys. Chem. B 111, 3055 (2007)]. Salt effects predicted by GBr(6)NL on 55 proteins overall deviate from NLPB counterparts by 0.5 kcal/mol from ionic strengths from 10 to 1000 mM, which is approximately 10% of the average magnitudes of the salt effects. GBr(6)NL predictions for the salts effects on the electrostatic interaction energies of two protein:RNA complexes are very promising.
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Affiliation(s)
- Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics, and School of Computational Science, Florida State University, Tallahassee, Florida 32306, USA
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24
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Abstract
The side chains of the 20 types of amino acids, owing to a large extent to their different physical properties, have characteristic distributions in interior/surface regions of individual proteins and in interface/non-interface portions of protein surfaces that bind proteins or nucleic acids. These distributions have important structural and functional implications. We have developed accurate methods for predicting the solvent accessibility of amino acids from a protein sequence and for predicting interface residues from the structure of a protein-binding or DNA-binding protein. The methods are called WESA, cons-PPISP and DISPLAR, respectively. The web servers of these methods are now available at http://pipe.scs.fsu.edu. To illustrate the utility of these web servers, cons-PPISP and DISPLAR predictions are used to construct a structural model for a multicomponent protein–DNA complex.
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Affiliation(s)
| | | | - Huan-Xiang Zhou
- *To whom correspondence should be addressed. +1 850 645 1336+1 850 644 7244
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25
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Abstract
The Poisson-Boltzmann (PB) equation is widely used for modeling electrostatic effects and solvation for macromolecules. The generalized Born (GB) model has been developed to mimic PB results at substantial lower computational cost. Here, we report an analytical GB method that reproduces PB results with high accuracy. The analytical approach builds on previous work of Gallicchio and Levy (J. Comput. Chem. 2004, 25, 479), and incorporates an improvement, proposed by Grycuk (J. Chem. Phys. 2003, 119, 4817), of the Coulomb-field approximation used in most GB methods. Tested against PB results, our GB method has an average unsigned relative error of only 0.6% for a representative set of 55 proteins and of 0.4% and 0.3%, respectively, for folded and unfolded conformations of cytochrome b562 sampled in molecular dynamics simulations. The dependencies of the electrostatic solvation free energy on solute and solvent dielectric constants and on salt concentration are fully accounted for in our method.
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Affiliation(s)
- Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics and School of Computational Science, Florida State University, Tallahassee, Florida 32306, USA
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Tjong H, Zhou HX. DISPLAR: an accurate method for predicting DNA-binding sites on protein surfaces. Nucleic Acids Res 2007; 35:1465-77. [PMID: 17284455 PMCID: PMC1865077 DOI: 10.1093/nar/gkm008] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Revised: 11/25/2006] [Accepted: 12/27/2006] [Indexed: 11/13/2022] Open
Abstract
Structural and physical properties of DNA provide important constraints on the binding sites formed on surfaces of DNA-targeting proteins. Characteristics of such binding sites may form the basis for predicting DNA-binding sites from the structures of proteins alone. Such an approach has been successfully developed for predicting protein-protein interface. Here this approach is adapted for predicting DNA-binding sites. We used a representative set of 264 protein-DNA complexes from the Protein Data Bank to analyze characteristics and to train and test a neural network predictor of DNA-binding sites. The input to the predictor consisted of PSI-blast sequence profiles and solvent accessibilities of each surface residue and 14 of its closest neighboring residues. Predicted DNA-contacting residues cover 60% of actual DNA-contacting residues and have an accuracy of 76%. This method significantly outperforms previous attempts of DNA-binding site predictions. Its application to the prion protein yielded a DNA-binding site that is consistent with recent NMR chemical shift perturbation data, suggesting that it can complement experimental techniques in characterizing protein-DNA interfaces.
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Affiliation(s)
| | - Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics and School of Computational Science, Florida State University, Tallahassee, FL 32306, USA
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Abstract
The Poisson-Boltzmann equation gives the electrostatic free energy of a solute molecule (with dielectric constant epsilon(l)) solvated in a continuum solvent (with dielectric constant epsilon(s)). Here a simple formula is presented that accurately predicts the electrostatic free energy for all combinations of epsilon(l) and epsilon(s) from the calculation on a single set of epsilon(l) and epsilon(s) values.
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Affiliation(s)
- Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics and School of Computational Science, Florida State University, Tallahassee, FL 32306, USA
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