scholarly journals Distinct histone H3–H4 binding modes of sNASP reveal the basis for cooperation and competition of histone chaperones

2021 ◽  
Author(s):  
Chao-Pei Liu ◽  
Wenxing Jin ◽  
Jie Hu ◽  
Mingzhu Wang ◽  
Jingjing Chen ◽  
...  
Keyword(s):  
De Novo ◽  
Critical Role ◽  
Histone H3 ◽  
Coiled Coil ◽  
Dynamic Network ◽  
Histone Chaperones ◽  
Binding Modes ◽  
Nucleosome Assembly ◽  
Partially Unfolded

Chromosomal duplication requires de novo assembly of nucleosomes from newly synthesized histones, and the process involves a dynamic network of interactions between histones and histone chaperones. sNASP and ASF1 are two major histone H3–H4 chaperones found in distinct and common complexes, yet how sNASP binds H3–H4 in the presence and absence of ASF1 remains unclear. Here we show that, in the presence of ASF1, sNASP principally recognizes a partially unfolded Nα region of histone H3, and in the absence of ASF1, an additional sNASP binding site becomes available in the core domain of the H3–H4 complex. Our study also implicates a critical role of the C-terminal tail of H4 in the transfer of H3–H4 between sNASP and ASF1 and the coiled-coil domain of sNASP in nucleosome assembly. These findings provide mechanistic insights into coordinated histone binding and transfer by histone chaperones.

scholarly journals Histone transfer among chaperones

2012 ◽  
Vol 40 (2) ◽  
pp. 357-363 ◽  
Author(s):  
Wallace H. Liu ◽  
Mair E.A. Churchill
Keyword(s):  
Histone H3 ◽  
Histone Chaperone ◽  
Chromatin Assembly ◽  
Histone Chaperones ◽  
Nucleosome Assembly ◽  
Post Translational Modifications ◽  
Chromatin Dynamics ◽  
Nucleosomal Dna ◽  
Chaperone Interactions ◽  
Dependent Processes

The eukaryotic processes of nucleosome assembly and disassembly govern chromatin dynamics, in which histones exchange in a highly regulated manner to promote genome accessibility for all DNA-dependent processes. This regulation is partly carried out by histone chaperones, which serve multifaceted roles in co-ordinating the interactions of histone proteins with modification enzymes, nucleosome remodellers, other histone chaperones and nucleosomal DNA. The molecular details of the processes by which histone chaperones promote delivery of histones among their many functional partners are still largely undefined, but promise to offer insights into epigenome maintenance. In the present paper, we review recent findings on the histone chaperone interactions that guide the assembly of histones H3 and H4 into chromatin. This evidence supports the concepts of histone post-translational modifications and specific histone chaperone interactions as guiding principles for histone H3/H4 transactions during chromatin assembly.

scholarly journals NAD+-Dependent Deacetylase Hst1p Controls Biosynthesis and Cellular NAD+ Levels in Saccharomyces cerevisiae

2003 ◽  
Vol 23 (19) ◽  
pp. 7044-7054 ◽  
Author(s):  
Antonio Bedalov ◽  
Maki Hirao ◽  
Jeffrey Posakony ◽  
Melisa Nelson ◽  
Julian A. Simon
Keyword(s):  
De Novo ◽  
Critical Role ◽  
Salvage Pathway ◽  
De Novo Synthesis ◽  
Array Analysis ◽  
Binding Partner ◽  
Dependent Protein ◽  
New Protein

ABSTRACT Nicotine adenine dinucleotide (NAD+) performs key roles in electron transport reactions, as a substrate for poly(ADP-ribose) polymerase and NAD+-dependent protein deacetylases. In the latter two processes, NAD+ is consumed and converted to ADP-ribose and nicotinamide. NAD+ levels can be maintained by regeneration of NAD+ from nicotinamide via a salvage pathway or by de novo synthesis of NAD+ from tryptophan. Both pathways are conserved from yeast to humans. We describe a critical role of the NAD+-dependent deacetylase Hst1p as a sensor of NAD+ levels and regulator of NAD+ biosynthesis. Using transcript arrays, we show that low NAD+ states specifically induce the de novo NAD+ biosynthesis genes while the genes in the salvage pathway remain unaffected. The NAD+-dependent deacetylase activity of Hst1p represses de novo NAD+ biosynthesis genes in the absence of new protein synthesis, suggesting a direct effect. The known Hst1p binding partner, Sum1p, is present at promoters of highly inducible NAD+ biosynthesis genes. The removal of HST1-mediated repression of the NAD+ de novo biosynthesis pathway leads to increased cellular NAD+ levels. Transcript array analysis shows that reduction in cellular NAD+ levels preferentially affects Hst1p-regulated genes in comparison to genes regulated with other NAD+-dependent deacetylases (Sir2p, Hst2p, Hst3p, and Hst4p). In vitro experiments demonstrate that Hst1p has relatively low affinity toward NAD+ in comparison to other NAD+-dependent enzymes. These findings suggest that Hst1p serves as a cellular NAD+ sensor that monitors and regulates cellular NAD+ levels.

scholarly journals Histone Chaperone Nap1 Is a Major Regulator of Histone H2A-H2B Dynamics at the InducibleGALLocus

2016 ◽  
Vol 36 (8) ◽  
pp. 1287-1296 ◽  
Author(s):  
Xu Chen ◽  
Sheena D'Arcy ◽  
Catherine A. Radebaugh ◽  
Daniel D. Krzizike ◽  
Holli A. Giebler ◽  
...  
Keyword(s):  
Critical Role ◽  
Histone Chaperones ◽  
Histone H2a ◽  
Nucleosome Assembly ◽  
Content Type ◽  
Nucleosome Assembly Protein ◽  
Nucleosome Assembly Protein 1 ◽  
Histone Exchange

Histone chaperones, like nucleosome assembly protein 1 (Nap1), play a critical role in the maintenance of chromatin architecture. Here, we use theGALlocus inSaccharomyces cerevisiaeto investigate the influence of Nap1 on chromatin structure and histone dynamics during distinct transcriptional states. When theGALlocus is not expressed, cells lacking Nap1 show an accumulation of histone H2A-H2B but not histone H3-H4 at this locus. Excess H2A-H2B interacts with the linker DNA between nucleosomes, and the interaction is independent of the inherent DNA-binding affinity of H2A-H2B for these particular sequences as measuredin vitro. When theGALlocus is transcribed, excess H2A-H2B is reversed, and levels of all chromatin-bound histones are depleted in cells lacking Nap1. We developed anin vivosystem to measure histone exchange at theGALlocus and observed considerable variability in the rate of exchange across the locus in wild-type cells. We recapitulate this variability within vitronucleosome reconstitutions, which suggests a contribution of DNA sequence to histone dynamics. We also find that Nap1 is required for transcription-dependent H2A-H2B exchange. Altogether, these results indicate that Nap1 is essential for maintaining proper chromatin composition and modulating the exchange of H2A-H2Bin vivo.

scholarly journals Heterozygous variants in KCNC2 cause a broad spectrum of epilepsy phenotypes associated with characteristic functional alterations

2021 ◽  
Author(s):  
Niklas Schwarz ◽  
Simone Seiffert ◽  
Manuela Pendziwiat ◽  
Annika Rademacher ◽  
Tobias Bruenger ◽  
...  
Keyword(s):  
Functional Analysis ◽  
De Novo ◽  
Critical Role ◽  
Specific Response ◽  
Loss Of Function ◽  
Causative Gene ◽  
Characteristic Functional ◽  
Research Collaborations ◽  
The Brain

Background KCNC2 encodes a member of the shaw-related voltage-gated potassium channel family (KV3.2), which are important for sustained high-frequency firing and optimized energy efficiency of action potentials in the brain. Methods Individuals with KCNC2 variants detected by exome sequencing were selected for clinical, further genetic and functional analysis. The cases were referred through clinical and research collaborations in our study. Four de novo variants were examined electrophysiologically in Xenopus laevis oocytes. Results We identified novel KCNC2 variants in 27 patients with various forms of epilepsy. Functional analysis demonstrated gain-of-function in severe and loss-of-function in milder phenotypes as the underlying pathomechanisms with specific response to valproic acid. Conclusion These findings implicate KCNC2 as a novel causative gene for epilepsy emphasizing the critical role of KV3.2 in the regulation of brain excitability with an interesting genotype-phenotype correlation and a potential concept for precision medicine.

scholarly journals Saccharomyces cerevisiae histone Chaperones FACT and Spt6 modulate Pol II and histone occupancy genome-wide

2018 ◽  
Author(s):  
Rakesh Pathak ◽  
Priyanka Singh ◽  
Sudha Ananthakrishnan ◽  
Sarah Adamczyk ◽  
Olivia Schimmel ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Critical Role ◽  
Histone Chaperones ◽  
Strongly Correlated ◽  
Pol Ii ◽  
Chromatin Remodelers ◽  
Coding Regions ◽  
Genome Wide ◽  
High Level

ABSTRACTHistone chaperones, chromatin remodelers, and histone modifying complexes play a critical role in alleviating the nucleosomal barrier. Here, we have examined the role of two highly conserved yeast (Saccharomyces cerevisiae) histone chaperones, FACT and Spt6, in regulating transcription and histone occupancy. We show that the H3 tail contributes to the recruitment of FACT to coding sequences in a manner dependent on acetylation. We found that deleting a H3 HAT Gcn5 or mutating lysines on the H3 tail impairs FACT recruitment at ADH1 and ARG1 genes. However, deleting the H4 tail or mutating the H4 lysines failed to dampen FACT occupancy in coding regions. Additionally, we show that FACT-depletion greatly reduces Pol II occupancy in the 5’ ends genome-wide. By contrast, Spt6-depletion led to reduction in Pol II occupancy towards the 3’ end, in a manner dependent on the gene-length. Severe transcription and histone eviction defects were also observed in a strain that was impaired for Spt6 recruitment (spt6Δ202) and depleted of FACT. Importantly, the severity of the defect strongly correlated with WT Pol II occupancies at these genes, indicating critical roles of Spt6 and Spt16 in promoting high-level transcription. Collectively, our study shows cooperation, as well as redundancy between chaperones, FACT and Spt6, in regulating transcription and chromatin in coding regions of transcribed genes.

scholarly journals The Critical Role of Tetrahydrobiopterin (BH4) Metabolism in Modulating Radiosensitivity: BH4/NOS Axis as an Angel or a Devil

2021 ◽  
Vol 11 ◽  
Author(s):  
Yang Feng ◽  
Yahui Feng ◽  
Liming Gu ◽  
Pengfei Liu ◽  
Jianping Cao ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Free Radicals ◽  
Ionizing Radiation ◽  
Molecular Mechanisms ◽  
De Novo ◽  
Antiangiogenic Therapy ◽  
Critical Role ◽  
Cellular Radiosensitivity ◽  
Normal Tissues

Ionizing radiation and radioactive materials have been widely used in industry, medicine, science and military. The efficacy of radiotherapy and adverse effects of normal tissues are closed related to cellular radiosensitivity. Molecular mechanisms underlying radiosensitivity are of significance to tumor cell radiosensitization as well as normal tissue radioprotection. 5,6,7,8-Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide synthases (NOS) and aromatic amino acid hydroxylases, and its biosynthesis involves de novo biosynthesis and a pterin salvage pathway. In this review we overview the role of BH4 metabolism in modulating radiosensitivity. BH4 homeostasis determines the role of NOS, affecting the production of nitric oxide (NO) and oxygen free radicals. Under conditions of oxidative stress, such as UV-radiation and ionizing radiation, BH4 availability is diminished due to its oxidation, which subsequently leads to NOS uncoupling and generation of highly oxidative free radicals. On the other hand, BH4/NOS axis facilitates vascular normalization, a process by which antiangiogenic therapy corrects structural and functional flaws of tumor blood vessels, which enhances radiotherapy efficacy. Therefore, BH4/NOS axis may serve as an angel or a devil in regulating cellular radiosensitivity. Finally, we will address future perspectives, not only from the standpoint of perceived advances in treatment, but also from the potential mechanisms. These advances have demonstrated that it is possible to modulate cellular radiosensitivity through BH4 metabolism.

scholarly journals TMCO1expression Promotes Cell Proliferation and Induces Epithelial-mesenchymal Transformation in Human Gliomas

2021 ◽  
Author(s):  
lun gao ◽  
Zhang Ye ◽  
Jun-Hui Liu ◽  
Ji-An Yang ◽  
Yong Li ◽  
...  
Keyword(s):  
Epithelial Mesenchymal Transition ◽  
Transmembrane Protein ◽  
Critical Role ◽  
Coiled Coil ◽  
World Health ◽  
Migration And Invasion ◽  
Who Grade ◽  
Mesenchymal Transition ◽  
Mesenchymal Transformation

Abstract Transmembrane and coiled-coil domains 1 (TMCO1) is a recently discovered transmembrane protein of endoplasmic reticulum (ER), which plays a critical role in maintaining calcium homeostasis. TMCO1 dysfunction has been proved to be closely related to a variety of human diseases, including glaucoma, deformities, mental retardation and tumorigenesis. However, the role of TMCO1 in gliomas remains unclear. The purpose of this study was to detect the role of TMCO1 in the pathogenesis and progression of gliomas. This study demonstrated that TMCO1 was up-regulated in gliomas and its overexpression predicted poor prognosis. We also revealed that the expression of TMCO1 was associated with the World Health Organization (WHO) grade of gliomas. Knockdown of TMCO1 inhibited the proliferation and induced apoptosis of U87 and U251cells. In addition, TMCO1 induced GBM cell migration and invasion by promoting epithelial-mesenchymal transition (EMT). These dates collectively proved the crucial role of TMCO1 as a novel prognostic factor and underlying therapeutic target for glioma patients.

scholarly journals Inhibiting adenine synthesis attenuates glioblastoma cell stemness and temozolomide resistance

2021 ◽  
Author(s):  
Simranjit X. Singh ◽  
Rui Yang ◽  
Kristen Roso ◽  
Landon J. Hansen ◽  
Changzheng Du ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Mitochondrial Function ◽  
Brain Cancer ◽  
De Novo ◽  
Critical Role ◽  
Glioblastoma Cell ◽  
Respiratory Capacity ◽  
Complementary Approach

Glioblastoma (GBM) is a lethal brain cancer exhibiting high levels of drug resistance, a feature partially imparted by tumor cell stemness. Recent work shows that homozygous MTAP deletion, a genetic alteration occurring in about half of all GBMs, promotes stemness in GBM cells. Exploiting MTAP loss-conferred deficiency in adenine salvage, we demonstrate that transient adenine blockade via treatment with L-Alanosine (ALA), an inhibitor of de novo adenine synthesis, attenuates stemness of MTAP-deficient GBM cells. This ALA-induced reduction in stemness is accompanied by compromised mitochondrial function, highlighted by diminished spare respiratory capacity. Direct pharmacological inhibition of mitochondrial respiration recapitulates the effect of ALA on GBM cell stemness, suggesting ALA targets stemness partially via affecting mitochondrial function. Finally, in agreement with diminished stemness and compromised mitochondrial function, we show that ALA sensitizes GBM cells to temozolomide (TMZ) in vitro and in an orthotopic GBM model. Collectively, these results identify critical roles of adenine supply in maintaining mitochondrial function and stemness of GBM cells, highlight a critical role of mitochondrial function in sustaining GBM stemness, and implicate adenine synthesis inhibition as a complementary approach for treating MTAP-deleted GBMs.

scholarly journals Histone chaperone FACT represses retrotransposon MERVL and MERVL-derived cryptic promoters

2020 ◽  
Vol 48 (18) ◽  
pp. 10211-10225 ◽  
Author(s):  
Fuquan Chen ◽  
Weiyu Zhang ◽  
Dan Xie ◽  
Tingting Gao ◽  
Zhiqiang Dong ◽  
...  
Keyword(s):  
Target Genes ◽  
Critical Role ◽  
Histone H3 ◽  
Embryonic Stem ◽  
Histone Chaperone ◽  
Endogenous Retroviruses ◽  
Histone Chaperones ◽  
Cryptic Transcription ◽  
Unique Mechanism ◽  
Cryptic Promoters

Abstract Endogenous retroviruses (ERVs) were usually silenced by various histone modifications on histone H3 variants and respective histone chaperones in embryonic stem cells (ESCs). However, it is still unknown whether chaperones of other histones could repress ERVs. Here, we show that H2A/H2B histone chaperone FACT plays a critical role in silencing ERVs and ERV-derived cryptic promoters in ESCs. Loss of FACT component Ssrp1 activated MERVL whereas the re-introduction of Ssrp1 rescued the phenotype. Additionally, Ssrp1 interacted with MERVL and suppressed cryptic transcription of MERVL-fused genes. Remarkably, Ssrp1 interacted with and recruited H2B deubiquitinase Usp7 to Ssrp1 target genes. Suppression of Usp7 caused similar phenotypes as loss of Ssrp1. Furthermore, Usp7 acted by deubiquitinating H2Bub and thereby repressed the expression of MERVL-fused genes. Taken together, our study uncovers a unique mechanism by which FACT complex silences ERVs and ERV-derived cryptic promoters in ESCs.

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