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Volpato A, Ollech D, Alvelid J, Damenti M, Müller B, York AG, Ingaramo M, Testa I. Extending fluorescence anisotropy to large complexes using reversibly switchable proteins. Nat Biotechnol 2023; 41:552-559. [PMID: 36217028 PMCID: PMC10110461 DOI: 10.1038/s41587-022-01489-7] [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: 10/05/2021] [Accepted: 08/26/2022] [Indexed: 11/08/2022]
Abstract
The formation of macromolecular complexes can be measured by detection of changes in rotational mobility using time-resolved fluorescence anisotropy. However, this method is limited to relatively small molecules (~0.1-30 kDa), excluding the majority of the human proteome and its complexes. We describe selective time-resolved anisotropy with reversibly switchable states (STARSS), which overcomes this limitation and extends the observable mass range by more than three orders of magnitude. STARSS is based on long-lived reversible molecular transitions of switchable fluorescent proteins to resolve the relatively slow rotational diffusivity of large complexes. We used STARSS to probe the rotational mobility of several molecular complexes in cells, including chromatin, the retroviral Gag lattice and activity-regulated cytoskeleton-associated protein oligomers. Because STARSS can probe arbitrarily large structures, it is generally applicable to the entire human proteome.
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Affiliation(s)
- Andrea Volpato
- Department of Applied Physics and Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Dirk Ollech
- Department of Applied Physics and Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Jonatan Alvelid
- Department of Applied Physics and Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Martina Damenti
- Department of Applied Physics and Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Barbara Müller
- Department of Infectious Diseases, Virology, Centre for Integrative Infectious Disease Research, University Hospital Heidelberg, Heidelberg, Germany
| | - Andrew G York
- Calico Life Sciences LLC, South San Francisco, CA, USA
| | | | - Ilaria Testa
- Department of Applied Physics and Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden.
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Ghoshal S, Chowdhury P, Ray S, Mitra M, Kanjilal SD, Sen S, Dasgupta AK, Sengupta S. Population genetic and biophysical evidences reveal that purifying selection shapes the genetic landscape of Plasmodium falciparum RH ligands in Chhattisgarh and West Bengal, India. Malar J 2020; 19:367. [PMID: 33054833 PMCID: PMC7557104 DOI: 10.1186/s12936-020-03433-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 10/01/2020] [Indexed: 11/17/2022] Open
Abstract
Background Reticulocyte binding protein-like homologs (RHs) are currently being evaluated as anti-erythrocytic stage vaccine targets against Plasmodium falciparum malaria. Present study explores the possible evolutionary drivers shaping the genetic organization of Pfrhs in Indian parasite population. It simultaneously evaluates a putative gain-of-function variant of PfRH5, a keystone member of PfRH family. Methods Receptor binding regions of Pfrh1, Pfrh2a/b, Pfrh4 and whole Pfrh5 were amplified using blood samples of P. falciparum malaria patients from Chhattisgarh and West Bengal and sequenced. Assembled sequences were analysed using MEGA7 and DnaSPv6. Binding affinities of recombinant PfRH5 proteins with basigin (BSG) were compared using in silico (CHARMM and AUTODOCK) and in vitro (Circular dichroism, fluorescence spectroscopy and isothermal titration calorimetry) methods. Results Pfrh1 (0.5), Pfrh2a/b (0.875), Pfrh4 (0.667) and Pfrh5 (0.778) sequence changes corresponded to low frequency (< 0.05) variants which resulted in an overall negative Tajima’s D. Since mismatch distribution of none of the Pfrh loci corroborated with the model of demographic expansion, a possible role of natural selection formulating Pfrh sequence diversity was investigated. Among the 5 members, Pfrh5 displayed very high dN/dS (5.7) ratio. Nevertheless, the model of selective sweep due to presence of any advantageous substitutions could not be invoked as polymorphic nonsynonymous sites (17/18) for Pfrh5 exceeded significantly over the divergent (62/86) ones (p = 0.0436). The majority of extant PfRH5 sequences (52/83) differed from the reference Pf3D7 allele by a single amino acid mismatch (C203Y). This non-conservative alteration was predicted to lower the total interaction energy of that PfRH5variant with BSG, compared to PfRH53D7. Biophysical evidences validated the proposition that PfRH5variant formed a more stable complex with BSG. Thermodynamic association constant for interaction of BSG with PfRH5variant was also found to be higher (Kavariant = 3.63E6 ± 2.02E6 M−1 and Ka3D7 = 1.31E6 ± 1.21E6 M−1). Conclusions Together, the study indicates that the genetic architecture of Pfrhs is principally shaped by purifying selection. The most abundant and ubiquitous PfRH5 variant harbouring 203Y, exhibits a greater affinity for BSG compared to PfRH53D7 possessing 203C allele. The study underscores the importance of selecting the functional allele that best represents circulating strains in natural parasite populations as vaccine targets.
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Affiliation(s)
- Sharmistha Ghoshal
- Department of Biochemistry, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700 019, West Bengal, India
| | - Pramita Chowdhury
- Department of Biochemistry, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700 019, West Bengal, India
| | - Sanhita Ray
- Department of Biochemistry, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700 019, West Bengal, India
| | - Mitashree Mitra
- School of Studies in Anthropology. Pt, Ravishankar Shukla University, Raipur, 492010, Chhattisgarh, India
| | - Sumana Datta Kanjilal
- Department of Pediatric Medicine, Institute of Post Graduate Medical Education & Research, Kolkata, West Bengal, India
| | - Srikanta Sen
- Mitra Tower, Lake Town, Block-A, Kolkata, 700 089, India
| | - Anjan Kr Dasgupta
- Department of Biochemistry, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700 019, West Bengal, India
| | - Sanghamitra Sengupta
- Department of Biochemistry, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700 019, West Bengal, India.
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Anisotropy-Based Nucleosome Repositioning Assay. Methods Mol Biol 2019; 1805:333-347. [PMID: 29971726 DOI: 10.1007/978-1-4939-8556-2_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Most eukaryotic DNA is tightly packaged into nucleosomes that render these sequences largely inaccessible for transcription or repair. Molecular motors called chromatin remodelers use an ATP-dependent mechanism to relieve the inhibition of these processes by sliding or disassembling the nucleosomes. This allows them to serve an essential role in the regulation of gene expression and genomic integrity. The sliding of nucleosomes along DNA can be studied directly by monitoring the associated changes in the fluorescence anisotropy of fluorophores attached to the ends of the DNA. Nucleosome repositioning can also be monitored indirectly through the ATP hydrolysis of the chromatin remodeler during the sliding reaction. Here we discuss how the kinetic data collected in these experiments can be analyzed by simultaneous global nonlinear least squares (NLLS) analysis using simple sequential "n-step" mechanisms to obtain estimates of the macroscopic rate of nucleosome repositioning and of the stoichiometry of coupling ATP binding and hydrolysis to this reaction.
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Al-Ani G, Briggs K, Malik SS, Conner M, Azuma Y, Fischer CJ. Quantitative determination of binding of ISWI to nucleosomes and DNA shows allosteric regulation of DNA binding by nucleotides. Biochemistry 2014; 53:4334-45. [PMID: 24898734 PMCID: PMC4100786 DOI: 10.1021/bi500224t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The
regulation of chromatin structure is controlled by a family
of molecular motors called chromatin remodelers. The ability of these
enzymes to remodel chromatin structure is dependent on their ability
to couple ATP binding and hydrolysis into the mechanical work that
drives nucleosome repositioning. The necessary first step in determining
how these essential enzymes perform this function is to characterize
both how they bind nucleosomes and how this interaction is regulated
by ATP binding and hydrolysis. With this goal in mind, we monitored
the interaction of the chromatin remodeler ISWI with fluorophore-labeled
nucleosomes and DNA through associated changes in fluorescence anisotropy
of the fluorophore upon binding of ISWI to these substrates. We determined
that one ISWI molecule binds to a 20 bp double-stranded DNA substrate
with an affinity of 18 ± 2 nM. In contrast, two ISWI molecules
can bind to the core nucleosome with short linker DNA with stoichiometric
macroscopic equilibrium constants: 1/β1 = 1.3 ±
0.6 nM, and 1/β2 = 13 ± 7 nM2. Furthermore,
to improve our understanding of the mechanism of DNA translocation
by ISWI, and hence nucleosome repositioning, we determined the effect
of nucleotide analogues on substrate binding by ISWI. While the affinity
of ISWI for the nucleosome substrate with short lengths of flanking
DNA was not affected by the presence of nucleotides, the affinity
of ISWI for the DNA substrate is weakened in the presence of nonhydrolyzable
ATP analogues but not by ADP.
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Affiliation(s)
- Gada Al-Ani
- Department of Molecular Biosciences, University of Kansas , 2034 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, United States
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Mechanism of CREB recognition and coactivation by the CREB-regulated transcriptional coactivator CRTC2. Proc Natl Acad Sci U S A 2012; 109:20865-70. [PMID: 23213254 DOI: 10.1073/pnas.1219028109] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Basic leucine zipper (bZip) transcription factors regulate cellular gene expression in response to a variety of extracellular signals and nutrient cues. Although the bZip domain is widely known to play significant roles in DNA binding and dimerization, recent studies point to an additional role for this motif in the recruitment of the transcriptional apparatus. For example, the cAMP response element binding protein (CREB)-regulated transcriptional coactivator (CRTC) family of transcriptional coactivators has been proposed to promote the expression of calcium and cAMP responsive genes, by binding to the CREB bZip in response to extracellular signals. Here we show that the CREB-binding domain (CBD) of CRTC2 folds into a single isolated 28-residue helix that seems to be critical for its interaction with the CREB bZip. The interaction is of micromolar affinity on palindromic and variant half-site cAMP response elements (CREs). The CBD and CREB assemble on the CRE with 2:2:1 stoichiometry, consistent with the presence of one CRTC binding site on each CREB monomer. Indeed, the CBD helix and the solvent-exposed residues in the dimeric CREB bZip coiled-coil form an extended protein-protein interface. Because mutation of relevant bZip residues in this interface disrupts the CRTC interaction without affecting DNA binding, our results illustrate that distinct DNA binding and transactivation functions are encoded within the structural constraints of a canonical bZip domain.
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ATP-independent cooperative binding of yeast Isw1a to bare and nucleosomal DNA. PLoS One 2012; 7:e31845. [PMID: 22359636 PMCID: PMC3281020 DOI: 10.1371/journal.pone.0031845] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 01/13/2012] [Indexed: 12/26/2022] Open
Abstract
Among chromatin remodeling factors, the ISWI family displays a nucleosome-enhanced ATPase activity coupled to DNA translocation. While these enzymes are known to bind to DNA, their activity has not been fully characterized. Here we use TEM imaging and single molecule manipulation to investigate the interaction between DNA and yeast Isw1a. We show that Isw1a displays a highly cooperative ATP-independent binding to and bridging between DNA segments. Under appropriate tension, rare single nucleation events can sometimes be observed and loop DNA with a regular step. These nucleation events are often followed by binding of successive complexes bridging between nearby DNA segments in a zipper-like fashion, as confirmed by TEM observations. On nucleosomal substrates, we show that the specific ATP-dependent remodeling activity occurs in the context of cooperative Isw1a complexes bridging extranucleosomal DNA. Our results are interpreted in the context of the recently published partial structure of Isw1a and support its acting as a “protein ruler” (with possibly more than one tick).
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Moyle-Heyrman G, Viswanathan R, Widom J, Auble DT. Two-step mechanism for modifier of transcription 1 (Mot1) enzyme-catalyzed displacement of TATA-binding protein (TBP) from DNA. J Biol Chem 2012; 287:9002-12. [PMID: 22298788 DOI: 10.1074/jbc.m111.333484] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The TATA box binding protein (TBP) is a central component of the transcription preinitiation complex, and its occupancy at a promoter is correlated with transcription levels. The TBP-promoter DNA complex contains sharply bent DNA and its interaction lifetime is limited by the ATP-dependent TBP displacement activity of the Snf2/Swi2 ATPase Mot1. Several mechanisms for Mot1 action have been proposed, but how it catalyzes TBP removal from DNA is unknown. To better understand the Mot1 mechanism, native gel electrophoresis and FRET were used to determine how Mot1 affects the trajectory of DNA in the TBP-DNA complex. Strikingly, in the absence of ATP, Mot1 acts to unbend DNA, whereas TBP remains closely associated with the DNA in a stable Mot1-TBP-DNA ternary complex. Interestingly, and in contrast to full-length Mot1, the isolated Mot1 ATPase domain binds DNA, and its affinity for DNA is nucleotide-dependent, suggesting parallels between the Mot1 mechanism and DNA translocation-based mechanisms of chromatin remodeling enzymes. Based on these findings, a model is presented for Mot1 that links a DNA conformational change with ATP-induced DNA translocation.
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Chen L, Zheng J, Yang N, Li H, Guo S. Genomic selection identifies vertebrate transcription factor Fezf2 binding sites and target genes. J Biol Chem 2011; 286:18641-9. [PMID: 21471212 DOI: 10.1074/jbc.m111.236471] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Identification of transcription factor targets is critical to understanding gene regulatory networks. Here, we uncover transcription factor binding sites and target genes employing systematic evolution of ligands by exponential enrichment (SELEX). Instead of selecting randomly synthesized DNA oligonucleotides as in most SELEX studies, we utilized zebrafish genomic DNA to isolate fragments bound by Fezf2, an evolutionarily conserved gene critical for vertebrate forebrain development. This is, to our knowledge, the first time that SELEX is applied to a vertebrate genome. Computational analysis of bound genomic fragments predicted a core consensus binding site, which identified response elements that mediated Fezf2-dependent transcription both in vitro and in vivo. Fezf2-bound fragments were enriched for conserved sequences. Surprisingly, ∼20% of these fragments overlapped well annotated protein-coding exons. Through loss of function, gain of function, and chromatin immunoprecipitation, we further identified and validated eomesa/tbr2 and lhx2b as biologically relevant target genes of Fezf2. Mutations in eomesa/tbr2 cause microcephaly in humans, whereas lhx2b is a critical regulator of cell fate and axonal targeting in the developing forebrain. These results demonstrate the feasibility of employing genomic SELEX to identify vertebrate transcription factor binding sites and target genes and reveal Fezf2 as a transcription activator and a candidate for evaluation in human microcephaly.
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Affiliation(s)
- Lishan Chen
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California 94158, USA
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Racki LR, Yang JG, Naber N, Partensky PD, Acevedo A, Purcell TJ, Cooke R, Cheng Y, Narlikar GJ. The chromatin remodeller ACF acts as a dimeric motor to space nucleosomes. Nature 2010; 462:1016-21. [PMID: 20033039 PMCID: PMC2869534 DOI: 10.1038/nature08621] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 10/29/2009] [Indexed: 01/01/2023]
Abstract
Evenly spaced nucleosomes directly correlate with condensed chromatin and gene silencing. The ATP-dependent chromatin assembly factor (ACF) forms such structures in vitro and is required for silencing in vivo. ACF generates and maintains nucleosome spacing by constantly moving a nucleosome towards the longer flanking DNA faster than the shorter flanking DNA. But how the enzyme rapidly moves back and forth between both sides of a nucleosome to accomplish bidirectional movement is unknown. We show that nucleosome movement depends cooperatively on two ACF molecules, suggesting that ACF functions as a dimer of ATPases. Further, the nucleotide state determines whether the dimer closely engages one vs. both sides of the nucleosome. Three-dimensional reconstruction by single particle electron microscopy of the ATPase-nucleosome complex in an activated ATP state reveals a dimer architecture in which the two ATPases face each other. Our results suggest a model in which the two ATPases work in a coordinated manner, taking turns to engage either side of a nucleosome, thereby allowing processive bidirectional movement. This novel dimeric motor mechanism differs from that of dimeric motors such as kinesin and dimeric helicases that processively translocate unidirectionally and reflects the unique challenges faced by motors that move nucleosomes.
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Affiliation(s)
- Lisa R Racki
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158, USA
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LiCata VJ, Wowor AJ. Applications of Fluorescence Anisotropy to the Study of Protein–DNA Interactions. Methods Cell Biol 2008; 84:243-62. [DOI: 10.1016/s0091-679x(07)84009-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Sahu SC, Swanson KA, Kang RS, Huang K, Brubaker K, Ratcliff K, Radhakrishnan I. Conserved themes in target recognition by the PAH1 and PAH2 domains of the Sin3 transcriptional corepressor. J Mol Biol 2007; 375:1444-56. [PMID: 18089292 DOI: 10.1016/j.jmb.2007.11.079] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 11/21/2007] [Accepted: 11/26/2007] [Indexed: 12/23/2022]
Abstract
The recruitment of chromatin-modifying coregulator complexes by transcription factors to specific sites of the genome constitutes an important step in many eukaryotic transcriptional regulatory pathways. The histone deacetylase-associated Sin3 corepressor complex is recruited by a large and diverse array of transcription factors through direct interactions with the N-terminal PAH domains of Sin3. Here, we describe the solution structures of the mSin3A PAH1 domain in the apo form and when bound to SAP25, a component of the corepressor complex. Unlike the apo-mSin3A PAH2 domain, the apo-PAH1 domain is conformationally pure and is largely, but not completely, folded. Portions of the interacting segments of both mSin3A PAH1 and SAP25 undergo folding upon complex formation. SAP25 binds through an amphipathic helix to a predominantly hydrophobic cleft on the surface of PAH1. Remarkably, the orientation of the helix is reversed compared to that adopted by NRSF, a transcription factor unrelated to SAP25, upon binding to the mSin3B PAH1 domain. The reversal in helical orientations is correlated with a reversal in the underlying PAH1-interaction motifs, echoing a theme previously described for the mSin3A PAH2 domain. The definition of these so-called type I and type II PAH1-interaction motifs has allowed us to predict the precise location of these motifs within previously experimentally characterized PAH1 binders. Finally, we explore the specificity determinants of protein-protein interactions involving the PAH1 and PAH2 domains. These studies reveal that even conservative replacements of PAH2 residues with equivalent PAH1 residues are sufficient to alter the affinity and specificity of these protein-protein interactions dramatically.
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Affiliation(s)
- Sarata C Sahu
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208-3500, USA
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