scholarly journals Insights into the Neutralization and DNA Binding of Toxin–Antitoxin System ParESO-CopASO by Structure-Function Studies

2021 ◽  
Vol 9 (12) ◽  
pp. 2506
Author(s):  
Juan Zhou ◽  
Xue-Jian Du ◽  
Ying Liu ◽  
Zeng-Qiang Gao ◽  
Zhi Geng ◽  
...  
Keyword(s):  
Dna Binding ◽  
Structure Function ◽  
Exothermic Reaction ◽  
Shewanella Oneidensis ◽  
Site Directed Mutagenesis ◽  
Regulation Mechanism ◽  
Intrinsically Disordered ◽  
New Type ◽  
Dna Binding Affinity ◽  
Positively Charged

ParESO-CopASO is a new type II toxin–antitoxin (TA) system in prophage CP4So that plays an essential role in circular CP4So maintenance after the excision in Shewanella oneidensis. The toxin ParESO severely inhibits cell growth, while CopASO functions as an antitoxin to neutralize ParESO toxicity through direct interactions. However, the molecular mechanism of the neutralization and autoregulation of the TA operon transcription remains elusive. In this study, we determined the crystal structure of a ParESO-CopASO complex that adopted an open V-shaped heterotetramer with the organization of ParESO-(CopASO)2-ParESO. The structure showed that upon ParESO binding, the intrinsically disordered C-terminal domain of CopASO was induced to fold into a partially ordered conformation that bound into a positively charged and hydrophobic groove of ParESO. Thermodynamics analysis showed the DNA-binding affinity of CopASO was remarkably higher than that of the purified TA complex, accompanied by the enthalpy change reversion from an exothermic reaction to an endothermic reaction. These results suggested ParESO acts as a de-repressor of the TA operon transcription at the toxin:antitoxin level of 1:1. Site-directed mutagenesis of ParESO identified His91 as the essential residue for its toxicity by cell toxicity assays. Our structure-function studies therefore elucidated the transcriptional regulation mechanism of the ParESO-CopASO pair, and may help to understand the regulation of CP4So maintenance in S. oneidensis.

scholarly journals X-linked thrombocytopenia with thalassemia from a mutation in the amino finger of GATA-1 affecting DNA binding rather than FOG-1 interaction

Blood ◽  
2002 ◽  
Vol 100 (6) ◽  
pp. 2040-2045 ◽  
Author(s):  
Channing Yu ◽  
Kathy K. Niakan ◽  
Mark Matsushita ◽  
George Stamatoyannopoulos ◽  
Stuart H. Orkin ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Zinc Fingers ◽  
Normal Function ◽  
Site Directed Mutagenesis ◽  
Erythroid Cells ◽  
Wild Type ◽  
Functional Consequences ◽  
Dna Binding Affinity ◽  
Erythroid Maturation

Abstract Transcription factor GATA-1 is essential for the development of erythroid cells and megakaryocytes. Each of its 2 zinc fingers is critical for normal function. The C-terminal finger is necessary for DNA binding. The N finger mediates interaction with FOG-1, a cofactor for GATA-1, and also modulates DNA-binding affinity, notably at complex or palindromic GATA sites. Residues of the N finger–mediating interaction with FOG-1 lie on the surface of the N finger facing away from DNA. Strong sequence conservation of residues facing DNA suggests that this other surface may also have an important role. We report here that a syndrome of X-linked thrombocytopenia with thalassemia in humans is caused by a missense mutation (Arg216Gln) in the GATA-1 N finger. To investigate the functional consequences of this substitution, we used site-directed mutagenesis to alter the corresponding residue in GATA-1. Compared with wild-type GATA-1, Arg216Gln GATA-1 shows comparable affinity to single GATA sites but decreased affinity to palindromic sites. Arg216Gln GATA-1 interacts with FOG-1 similarly with wild-type GATA-1. Arg216Gln GATA-1 supports erythroid maturation of GATA-1 erythroid cells, albeit at reduced efficiency compared with wild-type GATA-1. Together, these findings suggest that residues of the N finger of GATA-1–facing DNA contribute to GATA-1 function apart from interaction with the cofactor FOG-1. This is also the first example of β-thalassemia in humans caused by a mutation in an erythroid transcription factor.

scholarly journals Lowering DNA binding affinity of SssI DNA methyltransferase does not enhance the specificity of targeted DNA methylation in E. coli

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Krystyna Ślaska-Kiss ◽  
Nikolett Zsibrita ◽  
Mihály Koncz ◽  
Pál Albert ◽  
Ákos Csábrádi ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Dna Binding ◽  
Binding Affinity ◽  
Dna Methyltransferase ◽  
Restriction Enzymes ◽  
Dna Binding Protein ◽  
E Coli ◽  
Dna Binding Affinity ◽  
Higher Eukaryotes

AbstractTargeted DNA methylation is a technique that aims to methylate cytosines in selected genomic loci. In the most widely used approach a CG-specific DNA methyltransferase (MTase) is fused to a sequence specific DNA binding protein, which binds in the vicinity of the targeted CG site(s). Although the technique has high potential for studying the role of DNA methylation in higher eukaryotes, its usefulness is hampered by insufficient methylation specificity. One of the approaches proposed to suppress methylation at unwanted sites is to use MTase variants with reduced DNA binding affinity. In this work we investigated how methylation specificity of chimeric MTases containing variants of the CG-specific prokaryotic MTase M.SssI fused to zinc finger or dCas9 targeting domains is influenced by mutations affecting catalytic activity and/or DNA binding affinity of the MTase domain. Specificity of targeted DNA methylation was assayed in E. coli harboring a plasmid with the target site. Digestions of the isolated plasmids with methylation sensitive restriction enzymes revealed that specificity of targeted DNA methylation was dependent on the activity but not on the DNA binding affinity of the MTase. These results have implications for the design of strategies of targeted DNA methylation.

scholarly journals Slc7a11 Modulated by POU2F1 is Involved in Pigmentation in Rabbit

2019 ◽  
Vol 20 (10) ◽  
pp. 2493 ◽  
Author(s):  
Yang Chen ◽  
Shuaishuai Hu ◽  
Lin Mu ◽  
Bohao Zhao ◽  
Manman Wang ◽  
...  
Keyword(s):  
Skin Color ◽  
Site Directed Mutagenesis ◽  
Molecular Regulation ◽  
Luciferase Reporter ◽  
Directed Mutagenesis ◽  
Regulation Mechanism ◽  
Solute Carrier Family ◽  
Depth Analysis ◽  
Solute Carrier ◽  
Fur Color

Solute carrier family 7 member 11 (Slc7a11) is a cystine/glutamate xCT transporter that controls the production of pheomelanin pigment to change fur and skin color in animals. Previous studies have found that skin expression levels of Slc7a11 varied significantly with fur color in Rex rabbits. However, the molecular regulation mechanism of Slc7a11 in pigmentation is unknown. Here, rabbit melanocytes were first isolated and identified. The distribution and expression pattern of Slc7a11 was confirmed in skin from rabbits with different fur colors. Slc7a11 affected the expression of pigmentation related genes and thus affected melanogenesis. Meanwhile, Slc7a11 decreased melanocyte apoptosis, but inhibition of Slc7a11 enhanced apoptosis. Furthermore, the POU2F1 protein was found to bind to the −713 to −703 bp region of Slc7a11 promoter to inhibit its activity in a dual-luciferase reporter and site-directed mutagenesis assay. This study reveals the function of the Slc7a11 in melanogenesis and provides in-depth analysis of the mechanism of fur pigmentation.

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