scholarly journals How p53 Molecules Solve the Target DNA Search Problem: A Review

2020 ◽  
Vol 21 (3) ◽  
pp. 1031 ◽  
Author(s):  
Kiyoto Kamagata ◽  
Yuji Itoh ◽  
Dwiky Rendra Graha Subekti
Keyword(s):  
Dna Binding ◽  
Single Molecule ◽  
Search Problem ◽  
Target Search ◽  
Cellular Processes ◽  
Target Dna ◽  
Target Sites ◽  
Dna Strands ◽  
Single Molecule Studies

Interactions between DNA and DNA-binding proteins play an important role in many essential cellular processes. A key function of the DNA-binding protein p53 is to search for and bind to target sites incorporated in genomic DNA, which triggers transcriptional regulation. How do p53 molecules achieve “rapid” and “accurate” target search in living cells? The search dynamics of p53 were expected to include 3D diffusion in solution, 1D diffusion along DNA, and intersegmental transfer between two different DNA strands. Single-molecule fluorescence microscopy enabled the tracking of p53 molecules on DNA and the characterization of these dynamics quantitatively. Recent intensive single-molecule studies of p53 succeeded in revealing each of these search dynamics. Here, we review these studies and discuss the target search mechanisms of p53.

scholarly journals Guided nuclear exploration increases CTCF target search efficiency

2018 ◽  
Author(s):  
Anders S. Hansen ◽  
Assaf Amitai ◽  
Claudia Cattoglio ◽  
Robert Tjian ◽  
Xavier Darzacq
Keyword(s):  
Dna Binding ◽  
Single Molecule ◽  
Mammalian Cells ◽  
Rna Binding ◽  
Target Search ◽  
Single Molecule Tracking ◽  
Search Mechanism ◽  
Binding Factor ◽  
Target Sites ◽  
Mammalian Genomes

Mammalian genomes are enormous. For a DNA-binding protein, this means that the number of non-specific, off-target sites vastly exceeds the number of specific, cognate sites. How mammalian DNA-binding proteins overcome this challenge to efficiently locate their target sites is not known. Here through live-cell single-molecule tracking, we show that CCCTC-binding factor, CTCF, is repeatedly trapped in small zones in the nucleus in a manner that is largely dependent on its RNA-binding region (RBR). Integrating theory, we devise a new model, Anisotropic Diffusion through transient Trapping in Zones (ADTZ), to explain this. Functionally, transient RBR-mediated trapping increases the efficiency of CTCF target search by ∼2.5 fold. Since the RBR-domain also mediates CTCF clustering, our results suggest a “guided” mechanism where CTCF clusters concentrate diffusing CTCF proteins near cognate binding sites, thus increasing the local ON-rate. We suggest that local “guiding” may represent a general target search mechanism in mammalian cells.

scholarly journals Single Molecule Studies of DNA-Binding Proteins: Development of New Covalent DNA Anchoring Techniques for the Study of Rupture Forces of Replication Blocks

2014 ◽  
Vol 106 (2) ◽  
pp. 394a
Author(s):  
Richard Janissen ◽  
Bojk A. Berghuis ◽  
Orkide Ordu ◽  
Max M. Wink ◽  
David Dulin ◽  
...  
Keyword(s):  
Dna Binding ◽  
Single Molecule ◽  
Binding Proteins ◽  
Dna Binding Proteins ◽  
Single Molecule Studies

scholarly journals Cas12a is a dynamic and precise RNA-guided nuclease without off-target activity on λ-DNA

2021 ◽  
Author(s):  
Bijoya Paul ◽  
Loic Chaubet ◽  
Emma Verver ◽  
Guillermo Montoya
Keyword(s):  
Dna Binding ◽  
Genome Editing ◽  
Optical Tweezers ◽  
Target Site ◽  
Target Dna ◽  
Multiple Binding ◽  
Target Sites ◽  
Dna Binding And Cleavage ◽  
Target Activity ◽  
Insight Into

Cas12a is an RNA-guided endonuclease that is emerging as a powerful genome-editing tool. Here we combined optical tweezers with fluorescence to monitor Cas12a binding onto λ-DNA, providing insight into its DNA binding and cleavage mechanisms. At low forces Cas12a binds DNA specifically with two off-target sites, while at higher forces numerous binding events appear driven by the mechanical distortion of the DNA and partial matches to the crRNA. Despite the multiple binding events, cleavage is only observed on the target site at low forces, when the DNA is flexible. Activity assays show that the preferential off-target sites are not cleaved, and the λ-DNA is severed at the target site. This precision is also observed in Cas12a variants where the specific dsDNA and the unspecific ssDNA cleavage are dissociated or nick the target DNA. We propose that Cas12a and its variants are precise endonucleases that efficiently scan the DNA for its target but only cleave the selected site in the λ-DNA.

scholarly journals Biophysical characterization of DNA binding from single molecule force measurements

2010 ◽  
Vol 7 (3) ◽  
pp. 299-341 ◽  
Author(s):  
Kathy R. Chaurasiya ◽  
Thayaparan Paramanathan ◽  
Micah J. McCauley ◽  
Mark C. Williams
Keyword(s):  
Dna Binding ◽  
Single Molecule ◽  
Force Measurements ◽  
Biophysical Characterization

scholarly journals Watching cellular machinery in action, one molecule at a time

2016 ◽  
Vol 216 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Enrico Monachino ◽  
Lisanne M. Spenkelink ◽  
Antoine M. van Oijen
Keyword(s):  
Dynamic Behavior ◽  
Single Molecule ◽  
Protein Complexes ◽  
Imaging Techniques ◽  
Ensemble Averaging ◽  
Cellular Processes ◽  
Cellular Machinery

Single-molecule manipulation and imaging techniques have become important elements of the biologist’s toolkit to gain mechanistic insights into cellular processes. By removing ensemble averaging, single-molecule methods provide unique access to the dynamic behavior of biomolecules. Recently, the use of these approaches has expanded to the study of complex multiprotein systems and has enabled detailed characterization of the behavior of individual molecules inside living cells. In this review, we provide an overview of the various force- and fluorescence-based single-molecule methods with applications both in vitro and in vivo, highlighting these advances by describing their applications in studies on cytoskeletal motors and DNA replication. We also discuss how single-molecule approaches have increased our understanding of the dynamic behavior of complex multiprotein systems. These methods have shown that the behavior of multicomponent protein complexes is highly stochastic and less linear and deterministic than previously thought. Further development of single-molecule tools will help to elucidate the molecular dynamics of these complex systems both inside the cell and in solutions with purified components.

scholarly journals A conformational checkpoint between DNA binding and cleavage by CRISPR-Cas9

2017 ◽  
Author(s):  
Yavuz S. Dagdas ◽  
Janice S. Chen ◽  
Samuel H. Sternberg ◽  
Jennifer A. Doudna ◽  
Ahmet Yildiz
Keyword(s):  
Dna Binding ◽  
Single Molecule ◽  
Dna Cleavage ◽  
Genome Engineering ◽  
Divalent Cations ◽  
Guide Rna ◽  
Single Molecule Fret ◽  
Target Sites ◽  
Multiple Conformations ◽  
Dna Binding And Cleavage

AbstractThe Cas9 endonuclease is widely utilized for genome engineering applications by programming its single-guide RNA and ongoing work is aimed at improving the accuracy and efficiency of DNA targeting. DNA cleavage of Cas9 is controlled by the conformational state of the HNH nuclease domain, but the mechanism that governs HNH activation at on-target DNA while reducing cleavage activity at off-target sites remains poorly understood. Using single-molecule FRET, we identified an intermediate state of S. pyogenes Cas9, representing a conformational checkpoint between DNA binding and cleavage. Upon DNA binding, the HNH domain transitions between multiple conformations before docking into its active state. HNH docking requires divalent cations, but not strand scission, and this docked conformation persists following DNA cleavage. Sequence mismatches between the DNA target and guide RNA prevent transitions from the checkpoint intermediate to the active conformation, providing selective avoidance of DNA cleavage at stably bound off-target sites.

scholarly journals Structural Characterization of Transcription Factor C/EBPbeta

2014 ◽  
Vol 70 (a1) ◽  
pp. C1510-C1510
Author(s):  
Maria Miller
Keyword(s):  
Dna Binding ◽  
Biological Activities ◽  
Structural Basis ◽  
X Ray Crystallography ◽  
Cellular Processes ◽  
Disordered Protein ◽  
Eukaryotic Genes ◽  
Factor C ◽  
Structural Insights

The basic region:leucine zipper (bZIP) DNA-binding protein, C/EBPbeta, plays a central role in many vital cellular processes, but is also implicated in tumorigenesis, tumor progression, as well as viral replication within cells. C/EBPbeta binds to specific DNA sites as homo- or hetero-dimers and interacts with other transcription factors to control the transcription of a number of eukaryotic genes. C/EBPbeta is an intrinsically repressed protein that is activated in response to growth factors. This study employs a variety of techniques such as sequence analysis, molecular modeling, X-ray crystallography, and mutagenesis to provide structural insights into the mechanisms that modulate the biological activities of C/EBPbeta. Analysis of the primary structure indicates that C/EBPbeta is a largely disordered protein that consists of unstructured regions that have the potential to fold upon binding to molecular partners as well as regions that retain irregular conformations regardless of their environment. Here, a model of the auto-inhibited form of C/EBPbeta is presented as well as the structural basis of its specific dimerization, DNA-binding, and interactions with the p300 transcriptional co-activator.

scholarly journals Transient non-specific DNA binding dominates the target search of bacterial DNA-binding proteins

2020 ◽  
Author(s):  
Mathew Stracy ◽  
Jakob Schweizer ◽  
David J Sherratt ◽  
Achillefs N Kapanidis ◽  
Stephan Uphoff ◽  
...  
Keyword(s):  
Dna Binding ◽  
Single Molecule ◽  
Binding Proteins ◽  
Search Time ◽  
Dna Binding Proteins ◽  
Protein Diffusion ◽  
Chromosomal Dna ◽  
Dna Interactions ◽  
Target Search ◽  
Molecular Weights

ABSTRACTDespite their diverse biochemical characteristics and functions, all DNA-binding proteins share the ability to accurately locate their target sites among the vast excess of non-target DNA. Towards identifying universal mechanisms of the target search, we used single-molecule tracking of 11 diverse DNA-binding proteins in living Escherichia coli. The mobility of these proteins during the target search was dictated by DNA interactions, rather than by their molecular weights. By generating cells devoid of all chromosomal DNA, we discovered that the nucleoid does not pose a physical barrier for protein diffusion, but significantly slows the motion of DNA-binding proteins through frequent short-lived DNA interactions. The representative DNA-binding proteins (irrespective of their size, concentration, or function) spend the majority (58-99%) of their search time bound to DNA and occupy as much as ∼30% of the chromosomal DNA at any time. Chromosome-crowding likely has important implications for the function of all DNA-binding proteins.

Dark-Field Hyperspectral Imaging (DF-HSI) Modalities for Characterization of Single Molecule and Cellular Processes

2020 ◽  
pp. 231-262
Author(s):  
Nishir Mehta ◽  
Sushant Sahu ◽  
Shahensha Shaik ◽  
Ram Devireddy ◽  
Manas Ranjan Gartia
Keyword(s):  
Hyperspectral Imaging ◽  
Single Molecule ◽  
Dark Field ◽  
Cellular Processes
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