Biology subjects

Tang, Z.

Publications and source records attributed to Tang, Z..

141 records · Page 8Linked to original sources

bioRxiv2019

TAL1-mediated epigenetic modifications down-regulate the expression of GIMAP family in non-small cell lung cancer

BackgroudThe study was designed to explore the role of GIMAP family in non-small cell lung cancer (NSCLC) and its possible expression regulation mechanisms using existing biological databases including encyclopedia of DNA elements (ENCODE), gene expression omnibus (GEO), and the cancer genome atlas (TCGA).\n\nMethodsLung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD) were used to evaluate the expression of GIMAPs in TCGA. Five NSCLC datasets were then selected from GEO for validation. RNA-seq and Chip-seq data from ENCODE and GEO were used to observe epigenetic modifications on the chromosomes of GIAMPs in NSCLC. We constructed protein-protein interaction (PPI) network to reveal the main interacting proteins of GIMAPs. We then analyzed the correlation and regulatory mechanism between TAL1 and the expression of GIMAP family. We also used Kaplan-Meier for survival analysis.\n\nResultsAll 7 genes in the GIMAP family were down-regulated in NSCLC. H3K4me3 and H3K27ac disappeared, while H3K27me3 increased on the chromosome of this family. The expression of TAL1 was positively correlated with the expression of GIMAPs. sh-TAL1 significantly down-regulated the expression of GIMAP family through epigenetic modification. High expression of GIMAPs and TAL1 was found to be associated with a good prognosis of NLCSC.\n\nConclusionThe downregulation of TAL1 caused the disappearance of H3K27ac and H3K4me3. It also caused an increase in H3K27me3 on the GIMAPs gene, eventually leading to the overall downregulation of the GIMAP family genes.

bioinformatics↗

bioRxiv2019

uORFlight: a vehicle towards uORF-mediated translational regulation mechanisms in eukaryotes

Upstream open reading frames (uORFs) are prevalent in eukaryotic mRNAs. They act as a translational control element for precisely tuning the expression of the downstream major open reading frame (mORF) with essential cellular functionalities. uORF variation has been clearly associated with several human diseases. In contrast, natural uORF variants in plants have not ever been identified or linked with any phenotypic changes. The paucity of such evidence encouraged us to generate this database-uORFlight (http://uorflight.whu.edu.cn). It facilitates the exploration of uORF variation among different splicing models of Arabidopsis and rice genes. Most importantly, users can evaluate uORF frequency among different accessions at the population scale and find out the causal single nucleotide polymorphism (SNP) or insertion/deletion (INDEL) which can be associated with phenotypic variation through database mining or simple experiments. Such information will help to make hypotheses of uORF function in plant development or adaption to changing environments on the basis of the cognate mORF function. This database also curates plant uORF relevant literature into distinct groups. To be broadly interesting, our database expands uORF annotation into more species of fungi (Botrytis cinerea), plant (Brassica napus, Glycine max, Gossypium raimondii, Medicago truncatula, Solanum lycopersicum, Solanum tuberosum, Triticum aestivum and Zea mays), metazoan (Caenorhabditis elegans and Drosophila melanogaster) and vertebrate (Homo sapiens, Mus musculus and Danio rerio). Therefore, uORFlight will light up the runway toward how uORF genetic variation determines phenotypic diversity and advance our understanding of translational control mechanisms.

genomics↗

bioRxiv2019

Simplified Molecular Classification of Lung Adenocarcinomas Based on EGFR, KRAS, and TP53 Mutations

IntroductionGene expression profiling has consistently identified three molecular subtypes of lung adenocarcinoma that have prognostic implications. To facilitate stratification of patients with this disease into similar molecular subtypes, we developed and validated a simple, mutually exclusive classification.\n\nMethodsMutational status of EGFR, KRAS, and TP53 was used to define six mutually exclusive molecular subtypes. A development cohort of 283 cytology specimens of lung adenocarcinoma was used to evaluate the associations between the proposed classification and clinicopathologic variables including demographic characteristics, smoking history, fluorescence in situ hybridization and molecular results. For validation and prognostic assessment, 63 of the 283 cytology specimens with available survival data were combined with a separate cohort of 428 surgical pathology specimens of lung adenocarcinoma.\n\nResultsThe proposed classification yielded significant associations between these molecular subtypes and clinical and prognostic features. We found better overall survival in patients who underwent surgery and had tumors enriched for EGFR mutations. Worse overall survival was associated with older age, stage IV disease, and tumors with comutations in KRAS and TP53. Interestingly, neither chemotherapy nor radiation therapy showed benefit to overall survival.\n\nConclusionsThe mutational status of EGFR, KRAS, and TP53 can be used to easily classify lung adenocarcinoma patients into six subtypes that show a relationship with prognosis, especially in patients who underwent surgery, and these subtypes are similar to classifications based on more complex genomic methods reported previously.

cancer biology↗

bioRxiv2018

ChIA-PIPE: A fully automated pipeline for ChIA-PET data analysis and visualization

ChIA-PET enables the genome-wide discovery of chromatin interactions involving specific protein factors, with base-pair resolution. Interpreting ChIA-PET data depends on having a robust analytic pipeline. Here, we introduce ChIA-PIPE, a fully automated pipeline for ChIA-PET data processing, quality assessment, analysis, and visualization. ChIA-PIPE performs linker filtering, read mapping, peak calling, loop calling, chromatin-contact-domain calling, and can resolve allele-specific peaks and loops. ChIA-PIPE also automates quality-control assessment for each dataset. Furthermore, ChIA-PIPE generates input files for visualizing 2D contact maps with Juicebox and HiGlass, and provides a new dockerized visualization tool for high-resolution, browser-based exploration of peaks and loops. With minimal adjusting, ChIA-PIPE can also be suited for the analysis of other related chromatin-mapping data.

bioinformatics↗

bioRxiv2018

Interpretable classification of Alzheimer’s disease pathologies with a convolutional neural network pipeline

Neuropathologists assess vast brain areas to identify diverse and subtly-differentiated morphologies. Standard semi-quantitative scoring approaches, however, are coarse-grained and can lack precise neuroanatomic localization. We report a proof-of-concept deep learning pipeline identifying specific neuropathologies--amyloid plaques and cerebral amyloid angiopathy--in immunohistochemical-stained archival slides. Using automated segmentation of stained objects and a cloud-based interface, we annotated >70,000 plaque candidates from 43 whole slide images (WSIs) to train and evaluate convolutional neural networks. Networks achieved strong plaque classification (0.993 and 0.744 areas under the receiver operating characteristic and precision recall curve, respectively) on a 10 WSI hold-out set. Prediction confidence maps visualized morphology distributions from the full-WSI level down to 20x magnification. Resulting plaque-burden scores correlated well with established semi-quantitative scores. Finally, saliency mapping demonstrated that networks learned patterns agreeing with accepted pathologic features. This scalable means to augment a neuropathologists ability may suggest a route to neuropathologic deep phenotyping.

pathology↗

bioRxiv2018

Spatial Chromatin Architecture Alteration by Structural Variations in Human Genomes at Population Scale

This genome-wide study is focused on the impact of structural variants identified in individuals from 26 human populations onto three-dimensional structures of their genomes. We assess the tendency of structural variants to accumulate in spatially interacting genomic segments and design a high-resolution computational algorithm to model the 3D conformational changes resulted by structural variations. We show that differential gene transcription is closely linked to variation in chromatin interaction networks mediated by RNA polymerase II. We also demonstrate that CTCF-mediated interactions are well conserved across population, but enriched with disease-associated SNPs. Altogether, this study assesses the critical impact of structural variants on the higher order organization of chromatin folding and provides unique insight into the mechanisms regulating gene transcription at the population scale, among which the local arrangement of chromatin loops seems to be the leading one. It is the first insight into the variability of the human 3D genome at the population scale.

genomics↗

bioRxiv2018

Neural Modulation of Social Distance on Third-Party Punishment

As a crucial mechanism to enforce social norms, people as third parties tend to punish the norm violators even it costs their own pay-off. However, people do not usually treat everyone equally, e.g., it is shown that people are nice to close others. Here, we investigated how third party punishment (TPP) and its neural correlates is modulated by social distance (SD) by using fMRI. Behaviorally, participants punished more when the unfair perpetrator was more distant to them. Such SD-modulation effect was stronger when the punishment was free. Model-based results showed that SD-dependent computational signals were encoded in right dlPFC. More interestingly, SD modulated the relationship between punishment levels and neural activities in default network including vmPFC and bilateral hippocampus. The explorative functional connectivity analysis further showed that the vmPFC increased the association with left dlPFC when participants punished close others. Finally, punishment type (costly vs. free) also modulated the relationship between punishment levels and neural correlates in dACC and the ventral striatum. Taken together, our results revealed the neurocomputational underpinnings of how SD plays an important role in affecting TPP.

neuroscience↗

bioRxiv2017

The Tandem Duplicator Phenotype is a prevalent genome-wide cancer configuration driven by distinct gene mutations

The tandem duplicator phenotype (TDP) is a genome-wide instability configuration primarily observed in breast, ovarian and endometrial carcinomas. Here, we stratify TDP tumors by classifying their tandem duplications (TDs) into three span intervals, with modal values of 11 Kb, 231 Kb, and 1.7 Mb. TDPs with prominent ~11 Kb TDs feature the conjoint loss of TP53 and BRCA1. TDPs with ~231 Kb and ~1.7 Mb TDs associate with CCNE1 pathway activation or CDK12 disruptions, in conjunction with TP53 mutations. We prove the driver role of TP53 and BRCA1 abrogation for TDP induction by generating short-span TDP mammary tumors in genetically modified mouse models harboring deleterious mutations in only these two genes. Lastly, heterogeneous combinations of mutations mediated by TDs are selected for and contribute to the oncogenic burden of TDP tumors.

genomics↗

bioRxiv2017

Strong positive biodiversity-productivity relationships in a subtropical forest experiment

Forest ecosystems contribute substantially to global terrestrial primary productivity and climate regulation, but, in contrast to grasslands, experimental evidence for a positive biodiversity-productivity relationship in highly diverse forests is still lacking1. Here, we provide such evidence from a large forest biodiversity experiment with a novel design2 in subtropical China. Productivity (stand-level tree basal area, aboveground volume and carbon and their annual increment) increased linearly with the logarithm of tree species richness. Additive partitioning3 showed that increasing positive complementarity effects combined with weakening negative selection effects caused a strengthening of the relationship over time. In 2-species mixed stands, complementary effects increased with functional distance and selection effects with vertical crown dissimilarity between species. Understorey shrubs reduced stand-level tree productivity, but this effect of competition was attenuated by shrub species richness, indicating that a diverse understorey may facilitate overall ecosystem functioning. Identical biodiversity-productivity relationships were found in plots of different size, suggesting that extrapolation to larger scales is possible. Our results highlight the potential of multi-species afforestation strategies to simultaneously contribute to mitigation of climate change and biodiversity restoration.

ecology↗

bioRxiv2017

Evaluating the accuracy of the umbrella sampling plots with different dissociation paths, conformational changes, and structure preparation

The kinetics of ligand dissociation has been found to be crucial for a good drug candidate. Therefore, examining the underlying free energy profile of the dissociation that governs the kinetics becomes important. Umbrella sampling (US), a widely used free energy calculation method, has long been used to explore the dissociation process of ligand-receptor systems. The potential of mean force (PMF) computed from US seems to always produce binding affinity and energy barriers that more or less agree with experiments. However, such PMFs are influenced by many practical aspects, like the method used to generate the initial dissociation pathway, collective variables (CVs) that used to describe the reaction coordinate (RC), and how intensive the sampling is in the conformational space restrained by the CVs. These critical factors were rarely studied. Here we applied US to study the dissociation processes of {beta}-cyclodextrin ({beta}-CD) and p38 complex systems. For {beta}-CD, we used three different {beta}-CD conformations to generate the dissociation path manually. For p38, we generated the dissociation pathway using accelerated molecular dynamics (AMD) followed by conformational relaxing with short conventional molecular dynamics (MD), steered molecular dynamics (SMD) and manual pulling. We found that even for small {beta}-CD complexes, different {beta}-CD conformations will alter the height of the PMF and different dissociation directions result in appearance/disappearance of local minima. SMD poorly samples the residue sidechain movement, leading to overestimated height of PMF. On the other hand, the AMD pathway relaxed by short conventional MD sampled more accurate structures, resulting in reasonable PMF.

biophysics↗

bioRxiv2017

A QM/MM Study of Biomimetic Catalysis of Diels-Adler reactions Using Cyclodextrins

We performed computational research to investigate the mechanism by which cyclodextrins (CDs) catalyze Diels-Alder reactions between 9-anthracenemethanol and N-cyclohexylmaleimide. Hydrogen bonds (Hbonds) between N-cyclohexylmaleimide and the hydroxyl groups of cyclodextrins were suggested to play an important role in the catalysis.However, our free energy calculations and molecular dynamics simulations showed that these Hbonds are not stable, and quantum mechanics calculations suggested that the reaction is not promoted by these Hbonds. The binding of 9-anthracenemethanol and N-cyclohexylmaleimide to cyclodextrins was the key to the catalysis. Cyclodextrins act as a container to hold the two reactants in the cavity, pre-organizes them for the reactions, and thus reduces the entropy penalty to the activation free energy. Dimethyl-{beta}-CD was a better catalyst for this specific reaction than {beta}-CD because of its stronger van der Waals interaction with the pre-organized reactants and better performance in reducing the activation energy. This computational work sheds light on the mechanism of the catalytic reaction by cyclodextrins and introduces new perspectives of supramolecular catalysis.

biophysics↗

bioRxiv2017

A molecular dynamics investigation of CDK8/CycC and ligand binding: conformational flexibility and implication in drug discovery

The activities of CDK8 with partner Cyclin C (CycC) are a common feature of many diseases, especially cancers. Here we report the study of dynamic behaviors and energy profiles of 13 CDK8/CycC systems, including the DMG-in and DMG-out conformations as well as 5 type I ligands and 5 type II ligands, with all-atom unbiased molecular dynamics (MD) simulations. We observed numerous regional motions within CDK8, which move in concert to form five major protein motions. The motion of the activation loop doesnt appear to influence the binding of both types of ligands. Type I ligands remarkably reduce the motion of the C-terminal tail through the strong cation-{pi} interaction between the ligands and ARG356, and type II ligands stabilize the C helix by forming stable hydrogen bonds with GLU66. The MD calculations also confirmed the importance of CycC to the stability of the CDK8 system as well as the ligand binding. The MMPB/SA results show that van der Waals interaction is the main driving force for the binding of both types of ligands, but electrostatic energy and entropy penalty plays important roles in the binding of type II ligands. The volume analysis results indicate that the induced fitting theory applies in the binding of type I ligands. These results would help to improve the affinities of the existing ligands. Our MD work is complementary to crystal structures and may have implications in the development of new CDK8 inhibitors as well as in the field of drug discovery.

biophysics↗

bioRxiv2017

Energy Barriers, Molecular Motions, and Residence Time in Ligand Dissociation: A Computational Study on Type II Inhibitors Binding to CDK8/CycC

This study applies a novel computational strategy to investigate molecular recognition and binding kinetics using five pyrazolourea ligands dissociating from cyclin-dependent kinase 8 with cyclin C (CDK8/CycC) as an example. The computed free energy barriers guide designing compounds using the transient conformations unavailable in experiments. The intermediates and their free energy profile during ligand association and discussion processes control ligand-protein binding kinetics and bring a more complete picture of ligand-protein binding. We used metadynamics and a pathway search method to sample pathways and applied combined reduced dimensionality, molecular dynamics (MD) simulations and milestoning theory to construct the free energy profile and estimate the residence time. The binding free energy and the trend of binding kinetics agreed with experiments. We explain the why of the barriers and the kinetics and use the information to assist ligand design. Guided by a barrier of a ligand passing an C helix and activation loop, we introduced one hydroxyl group to parent compounds to design our ligands with increased residence time and validated our prediction by experiments. This work provides a novel and robust approach to investigate dissociation kinetics of large and flexible systems for understanding unbinding mechanisms and designing new small molecule drugs with desired binding kinetics.\n\nSignificance StatementThe transient conformations during ligand binding/unbinding control non-covalent binding kinetics. However, the transient structures and their free energy landscape of flexible ligand-protein systems are unavailable in experiments and challenging to model. Due to lack of understanding in binding kinetics, even scientists know that kinetic properties can be important in drug development, calculations using the intermediate states to design ligands with preferred binding kinetics are absent. We overcome these challenges and compute ligand-protein unbinding free energy profile using a novel method with molecular dynamics simulations, reduced dimensionality, and milestoning theory to deepen our understanding in molecular recognition. We also designed compounds based on the computed free energy barriers and experimentally validated that our designed compound can increase residence time.

biophysics↗

bioRxiv2017

Binding Thermodynamics and Kinetics Calculations Using Chemical Host and Guest: A Comprehensive Picture of Molecular Recognition

Understanding the fine balance between changes of entropy and enthalpy and the competition between a guest and water molecules in molecular binding is crucial in fundamental studies and practical applications. Experiments provide measurements. However, illustrating the binding/unbinding processes gives a complete picture of molecular recognition not directly available from experiments, and computational methods bridge the gaps. Here, we investigated guest association/dissociation with {beta}-cyclodextrin ({beta}-CD) by using microsecond-timescale molecular dynamics (MD) simulations, post-analysis and numerical calculations. We computed association and dissociation rate constants, enthalpy, and solvent and solute entropy of binding. All the computed values of kon, koff, {Delta}H, {Delta}S, and {Delta}G using GAFF-CD and q4MD-CD force fields for {beta}-CD could be compared with experimental data directly and agreed reasonably with experiment findings. Both force fields resulted in similar computed {Delta}G from independently computed kinetics rates, {Delta}G=-RTln(kon {middle dot} C{degrees} / k off), and thermodynamics properties, {Delta}G={Delta}H - T{Delta}S. The water entropy calculations show that entropy gain of desolvating water molecules are a major driving force, and both force fields have the same strength of non-polar attractions between solutes and {beta}-CD as well. Water molecules play a crucial role in guest binding to {beta}-CD. However, collective water/{beta}-CD motions could contribute to different computed kon and {Delta}H values by different force fields, mainly because the parameters of {beta}-CD provide different motions of {beta}-CD, hydrogen-bond networks of water molecules in the cavity of free {beta}-CD and the strength of desolvation penalty. As a result, q4MD-CD suggests that guest binding is mostly driven by enthalpy, while GAFF-CD shows that gaining entropy is the major driven force of binding. The study further interprets experiments, deepens our understanding of ligand binding, and suggests strategies for force field parameterization.

biophysics↗

bioRxiv2017

Human to yeast pathway transplantation: cross-species dissection of the adenine de novo pathway regulatory node

Pathway transplantation from one organism to another represents a means to a more complete understanding of a biochemical or regulatory process. The purine biosynthesis pathway, a core metabolic function, was transplanted from human to yeast. We replaced the entire Saccharomyces cerevisiae adenine de novo pathway with the cognate human pathway components. A yeast strain was \"humanized\" for the full pathway by deleting all relevant yeast genes completely and then providing the human pathway in trans using a neochromosome expressing the human protein coding regions under the transcriptional control of their cognate yeast promoters and terminators. The \"humanized\" yeast strain grows in the absence of adenine, indicating complementation of the yeast pathway by the full set of human proteins. While the strain with the neochromosome is indeed prototrophic, it grows slowly in the absence of adenine. Dissection of the phenotype revealed that the human ortholog of ADE4, PPAT, shows only partial complementation. We have used several strategies to understand this phenotype, that point to PPAT/ADE4 as the central regulatory node. Pathway metabolites are responsible for regulating PPATs protein abundance through transcription and proteolysis as well as its enzymatic activity by allosteric regulation in these yeast cells. Extensive phylogenetic analysis of PPATs from diverse organisms hints at adaptations of the enzyme-level regulation to the metabolite levels in the organism. Finally, we isolated specific mutations in PPAT as well as in other genes involved in the purine metabolic network that alleviate incomplete complementation by PPAT and provide further insight into the complex regulation of this critical metabolic pathway.

synthetic biology↗