Abstract:rDNA is an array of tandemly repeated genes controlling cellular ribosomes’ biosynthesis, therefore determining translational level of overall proteins and being closely linked with cellular growth and metabolism. Because of the multi-copy feature, the transcription activity of rDNA repeats is not only adjusted by general transcription mechanism, but also finely regulated by multiple epigenetic mechanisms. Generally, rDNA is divided into two epigenetic states, active and silent state, relating to active chromatin marks and heterochromatin marks respectively. In recent years, a poise state has been found, which enriches the research of epigenetic mechanism in rDNA regulation. H3.3, a hot topic in recent years, is a variant of histone H3, which has been reported that might incorporate into active rDNA by its chaperone HIRA. However, more devotion is required to explore whether silent rDNA is maintained by H3.3 as well. Another regulator is CTCF, an insulator component that occupying between repeated rDNA units. Whether CTCF is involved in regulating the transcription of rDNA is still unknown. In this review, we present our current knowledge of the mechanisms in rDNA epigenetic regulation, and propose new hypotheses of regulatory mechanism that might exist in this process.

Abstract:The aging of the population is a global challenge. The number of older adults is rapidly growing, leading to an increase in the prevalence of noncommunicable diseases associated with aging, such as cancer. Almost two-thirds of all new cancer diagnoses are over 65 years, and this proportion is projected to increase globally. Cellular senescence is a state of stable growth arrest induced by DNA damage or dysregulation of oncogene, coupled with the morphological, biochemical, and epigenetical changes. Increasingly evidences have demonstrated that cell senescence might be an important mechanism for suppressing tumorigenesis. Recently, however it has become apparent that this process entails more than a simple cessation of cell growth, cellular senescence might also promote cancer progression. Which leading to the concept that cellular senescence can play as a double-edged sword in the fight against cancer. Therefore, in depth understanding of the relationship between cell senescence and tumor, and making full use of the antagonize effect of cellular senescence on tumor and avoiding its role in promoting the tumor may give us another potential choices for tumor therapy.

Abstract:Mitochondria are important intracellular organelles that not only provide energy for cellular activities via oxidative phosphorylation, but also closely associated with some important biological processes, including cell metabolism, stress signaling induction, calcium homeostasis, production of reactive oxygen species (ROS) and apoptosis．Mitochondrial dysfunction will lead to tumor development, growth, invasion and metastasis．Mitochondrial quality control system has become a key mechanism that maintains the normal function of the mitochondria, which is mainly composed of organellar and molecular control．Organellar quality control was coordinately modulated by mitochondrial fusion/fission, mitophagy and mitochondrial biogenesis．Meanwhile, molecular quality control was regulated by mitochondrial molecular chaperones and mitochondrial unfolded protein response to achieve mitochondrial protein homeostasis．In normal circumstances, mitochondrial quality control system limits the accumulation of dysfunctional mitochondria and maintains mitochondrial quantity, morphology and protein function in stable state, which was called mitochondrial homeostasis．If the mitochondrial homeostasis is impaired, increased number of injured mitochondria in cells will lead to the disturbance of intracellular homeostasis and induce malignant transformation of normal cells．

Abstract:Cyclin-dependent kinase Cdk1 is the master regulator on eukaryotic cell cycle control and crucial for prevention of genomic instability. Given its essential function in cell cycle progression, Cdk1 is tightly regulated. Among others, CDK inhibitors (CKIs) are important negative factors for CDK activity regulation, lack of which leads to uncontrolled cell division and promotes tumorigenesis. The model eukaryotic organism Saccharomyces cerevisiae, budding yeast, in many respects is an ideal organism for eukaryotic CDK regulation research. In budding yeast three Cdk1 inhibitors are known: Far1, Sic1 and recently identified Cip1. Apart from inhibiting Cdk1 activity during cell cycle progression, CKIs also play crucial roles to maintain genomic stability in response to environmental stresses. This paper reviewed the researches on Cdk1 inhibitors, especially their functions on cell cycle progression and stress responses, to provide a model basis for cell cycle and cancer fundamental research.

Abstract:The engineered ascorbate peroxidase (APEX) developed by Alice Ting laboratory, compared with classical horse radish peroxidase (HRP), can keep active within all cellular compartments, so it has great potential as a tool for studying the fusion proteins in both subcellular organelles and live cells. Up to now, diaminobenzidine staining based on APEX tag has been successfully developed for electron microscopy (EM) in whole cells, subcellular organelles and proteins. Moreover, combined with mass spectrometry technique, APEX-mediated proximity biotin labeling in living cells greatly promoted the study of subcellular organelle proteomics and temporal-spatial proteomics. This review focused on the principle of APEX methodology, summarized its latest applications including EM imaging and spatial proteomics, and discussed its limitations and challenges as well.

Abstract:The membrane potential of a cell is produced by the difference between intracellular and extracellular ion concentrations, which can be categorized into either resting potential or action potential. Voltage clamp and patch clamp are the main techniques to detect and record the membrane potential. And the electrode in the voltage clamp and glass tube in the patch clamp can stimulate the cell membrane and can’t monitor or record the potential online. Cell-field effect transistor is a kind of sensor for membrane potential detection which controls the leakage source current of the device at the grid, so as to sense the membrane potential of cell. It is a new technology of membrane potential detection and record, and its advantage is that detecting without stimulation to the cell membrane, and monitoring at real time for a long time length. And it can be widely applied to the fields such as scientific research, drug development, medical device, inspection and quarantine, environmental protection, public security, and so on. This paper introduced the structure, transfer characteristic, equivalent circuit, preparation technology of the cell-FET sensor, and application in action potential recording, real-time monitoring of cell growth, monitoring of exocytosis, and detecting of tumor biomarker.

Abstract:The default mode network (DMN) has been reported to be involved in a variety of important cognitive functions and received increasing attention in neuroscience recently. Its dysfunction is also reported to be associated with multiple psychiatric disorders. However, the causal information flow (effective connectivity) within the default mode network remains poorly understood. In this study, we explored the effective connectivity pattern between 4 key DMN brain areas based on a high resolution 7T resting state fMRI dataset using a cutting-edge spectral dynamic causal modelling technique. Results showed that there was a distinct effective connectivity pattern among the DMN nodes. We found medial prefrontal cortex(MPFC) and bilateral inferior parietal cortex(IPC) sent information to the posterior cingulate cortex(PCC), which suggested that the PCC might be a hub region that collected information from other DMN areas. Besides, a causal influence was found from bilateral IPC to MPFC, and from left IPC to right IPC. This work was the first 7T fMRI study that investigated effective connectivity pattern among DMN nodes, which may promote our understandings about the functions of DMN and benefit future research in DMN-related psychiatric disorders.

Abstract:To investigate the role of miR-33s in the inhibition of ATP-binding cassette transporter A1 (ABCA1) expression and cholesterol efflux induced by NF-κB, THP-1 macrophage-derived foam cells were treated with different concentrations of LPS to activate NF-κB with or without PDTC (NF-κB inhibitors)，the mRNA expression of miR-33s and its host gene SREBPs were detected by RT-PCR, the proteins expression of SREBPs were detected by Western blot, the binding capacifies of NF-κB p65 to SREBPs promoters were detected by chromatin immunoprecipitation. After cells were treated with LPS, miR-33s inhibitor or mimic were transfected, ABCA1 mRNA and protein were detected by RT-PCR and Western blot, respectively. The cholesterol efflux was detected by liquid scintillation counter. The results showed that expression of miR-33s and SREBPs were increased by NF-κB activation and decreased by adding PDTC. NF-κB p65 could directly combine with the SREBPs promoter. After transfected with miR-33s inhibitor, the inhibitory effect of NF-κB activation on ABCA1 expression was weakened, and cholesterol efflux was increased. On the contrary, the inhibitory effect on ABCA1 strengthened and cholesterol efflux decreased after transfected by miR-33s mimic. These results suggested that NF-κB activation could promote miR-33s expression, inhibit ABCA1 expression and cholesterol efflux.

Abstract:The enzyme molecule is natural effective biological catalyst. The enzyme - substrate (ES) complex forming in the first step imparts the catalytic efficiency of enzyme. Specifically, multiple amino acid residues composed the active site of enzyme, which created a precisely organized architecture for substrate recognition, binding and catalytic process. Therefore, the function of amino acid residues in active-site architecture has always been the research hotspot in protein engineering. The enzymes in GH11 and GH12 families have small molecular mass and large range of enzymology properties, which are good candidates to study the binding affinity of enzymes. In this study, the catalytic activity and band mobility of different mutants in the active-site architecture of TrCel12A and TlXynA could be rapidly demonstrated by affinity electrophoresis. The substrate binding affinity can be quantitatively characterized by quantitative regression analysis of the relative mobility of proteins at different substrate concentrations. At the same time, isothermal titration calorimetry and fluorescence spectroscopy were also used to determine the binding affinity of different mutants. For the mutants of TrCel12A, the parameters K_b measured by affinity electrophoresis were significantly related with those determined by isothermal titration calorimetry (R² = 0.82) and fluorescence spectroscopy (R² = 0.83). Therefore, the magnitude of their affinities was TrCel12A-E200Q>W22YE200Q>W22FE200Q>W22HE200Q>W22AE200Q, respectively. Furthermore, the substrate binding affinities of the variants in TlXynA were also characterized using affinity electrophoresis. The results showed that there was a good correlation with that measured by fluorescence spectrometry (R² = 0.84). These results indicate that the parameters K_b measured by affinity electrophoresis can characterize the binding ability influenced by amino acid single-point mutation in active-site architecture of glucoside hydrolase. Therefore, affinity electrophoresis was effective and can be used as routine screening technology in biochemical laboratory to detect the change of series mutants binding affinity in mutant library.