Maintaining cholesterol homeostasis: Sterol regulatory element-binding proteins

The molecular mechanism of how hepatocytes maintain cholesterol homeostasis has become much more transparent with the discovery of sterol regulatory element binding proteins (SREBPs) in recent years. These membrane proteins aremembers of the basic helix-loop-helix-leucine zipper (bHLHZip) family of transcription factors. They activate the expression of at least 30 genes involved in the synthesis of cholesterol and lipids. SREBPs are synthesized as precursor proteins in the endoplasmic reticulum (ER), where they form a complex with another protein, SREBP cleavage activating protein (SCAP). The SCAP molecule contains a sterol sensory domain. In the presence of high cellular sterol concentrations SCAP confines SREBP to the ER. With low cellular concentrations, SCAP escorts SREBP to activation in the Golgi. There, SREBP undergoes two proteolytic cleavage steps to release the mature, biologically active transcription factor, nuclear SREBP (nSREBP). nSREBP translocates to the nucleus and binds to sterol response elements (SRE) in the promoter/enhancer regions of target genes. Additional transcription factors are required to activate transcription of these genes. Three different SREBPs are known, SREBPs-1a, -1c and -2. SREBP-1a and -1c are isoforms produced from a single gene by alternate splicing. SREBP-2 is encoded by a different gene and does not display any isoforms. It appears that SREBPs alone, in the sequence described above, can exert complete control over cholesterol synthesis, whereas many additional factors (hormones, cytokines, etc.) are required for complete control of lipid metabolism. Medicinal manipulation of the SREBP/SCAP system is expected to prove highly beneficial in the management of cholesterol-related disease.

Screening of Extracellular Binding Proteins of Rice Receptor-like Kinase CR4 by the Yeast Two-hybrid

[Objective] The research aimed to find the extracellular binding proteins of CR4.[Method] The extracellular domain of OsCR4 was as the bait protein,and the yeast two-hybrid was used to screen cDNA library of seedling which was cultivated 14 d.[Result] A lot of proteins which included a peroxide B（D26484）,a methionine thioredoxin reductase（ABF96078）and an unknown function protein were gained.[Conclusion] It provided the theory basis for studying the signal transduction mechanism of CR4.

Advances on Plant Pathogenic Mycotoxin Binding Proteins

Toxin-binding protein is one of the key subjects in plant pathogenic mycotoxin research. In this paper, new advances in toxin-binding proteins of 10 kinds of plant pathogenic mycotoxins belonging to Hel-minthosporium,Alternaria,Fusicoccum,Verticillium were reviewed, especially the techniques and methods of toxin-binding proteins of HS-toxin, HV-toxin, HMT-toxin, HC-toxin. It was proposed that the isotope-labeling technique and immunological chemistry technique should be combined together in research of toxin-binding protein, which will be significant to study the molecular recognition mechanism between host and pathogenic fungus.

Identification of AOSC-binding proteins in neurons

Acidic oligosaccharide sugar chain （AOSC）, a D-mannuronic acid oligosaccharide, derived from brownalgaepolysaccharide, has been completed Phase I clinical trial in China as an anti-Alzheimer＇s Disease （AD） drug candidate. The identification of AOSC-binding protein（s） in neurons is very important for understanding its action mechanism. To determine the binding protein（s） of AOSC in neurons mediating its anti-AD activities, confocal microscopy, affinity chromatography, and liquid chromatography-tandem mass spectrometry （LC-MS/MS） analysis were used. Confocal microscopy analysis shows that AOSC binds to SH-SY5Y cells in concentration-, time-, and temperature-dependent fashions. The AOSC binding proteins were purified by affinity chromatography and identified by LC-MS/MS analysis. The results showed that there are 349 proteins binding AOSC, including clathrin, adaptor protein-2 （AP-2） and amyloid precursor protein （APP）. These results suggest that the binding/entrance of AOSC to neurons is probably responsible for anti-AD activities.

Cysteine Residues in Receptor Proteins： Structural Insights from Two E. coil Periplasmic Binding Proteins

Cysteine residues found in proteins have various functions such as metal binding, nitrosylation, and stabilization of structure. We have done a comparative, computational structural analysis of the cysteine residues in two proteins from bacteria to get some insight into the differences between metal binding cysteine residues and those involved in structure stabilization. The two target proteins in this study are the periplasmic mercury binding protein （MerP） and the 1-1eucine binding protein （LBP）. Both are periplasmic binding proteins from E. coli. We have shown key phenomenon that define cysteines as metal binding or structural in nature.

Novel Treatment Approach in Schizophrenia: Substitution of Glial Binding Proteins

In chronic schizophrenia, synaptic information processing is unbalanced, as shown in a model of glial-neuronal synaptic units, called tripartite synapses. The glial component of the synapse exerts a modifying function in neurotransmission since the astrocyte activated by neurotransmitters produces gliotransmitters that negatively feedback to the presynapse. It is hypothesized that in schizophrenia nonfunctional astrocytic receptors cannot be activated, thus losing their modulating function. This causes a generalization of information processing in the neuronal networks such that the brain is unable to distinguish between subjects and objects in the environment. Delusions, hallucinations and cognitive impairment occur on the behavioral level. In a model of a cholinergic tripartite synapse, it is shown that glial binding proteins modify neurotransmission by occupancy with cognate neurotransmitters temporarily turning off neurotransmission on the presynapse. Most recently, glial binding proteins have been engineered. It is proposed that the substitution of glial binding proteins may balance synaptic information processing in schizophrenia since these proteins exert a modulatory function comparable to functional astrocytic receptors. Rap- id technical developments may enable this novel treatment approach in schizophrenia.

The RNA binding proteins TIA1 and TIAL1 promote Mcl1 mRNA translation to protect germinal center responses from apoptosis

Germinal centers(GCs)are essential for the establishment of long-lasting antibody responses.GC B cells rely on post-transcriptional RNA mechanisms to translate activation-associated transcriptional programs into functional changes in the cell proteome.However,the critical proteins driving these key mechanisms are still unknown.Here,we show that the RNA binding proteins TIA1 and TIAL1 are required for the generation of long-lasting GC responses.TIA1-and TIAL1-deficient GC B cells fail to undergo antigen-mediated positive selection,expansion and differentiation into B-cell clones producing high-affinity antibodies.Mechanistically,TIA1 and TIAL1 control the transcriptional identity of dark-and light-zone GC B cells and enable timely expression of the prosurvival molecule MCL1.Thus,we demonstrate here that TIA1 and TIAL1 are key players in the post-transcriptional program that selects high-affinity antigen-specific GC B cells.

Targeted Degradation of DNA/RNA Binding Proteins via Covalent Hydrophobic Tagging

Targeted protein degradation(TPD)holds great promise for biological inquiry and therapeutic development.However,it still remains elusive to destruct DNA/RNA binding proteins(DBPs/RBPs)previously deemed undruggable.Herein,we report ligandassisted covalent hydrophobic tagging(LACHT)as a modular strategy for TPD of these difficult-totarget proteins.Guided by a noncovalent protein ligand,LACHT leverages a reactive N-acyl-N-alkyl sulfonamide group to covalently label the protein target with a hydrophobic adamantane,which further engages the cellular quality control mechanism to induce proteolytic degradation.Using a smallmolecule ligand,we demonstrated that LACHT allowed TPD of a DBP,bromodomain-containing protein 4,in human leukemia cells with high efficiency.Mechanistic studies revealed that LACHT-mediated TPD dependent on ligand-directed irreversible tagging and the covalently labeled proteins underwent polyubiquitination before removal through both the proteasome and the lysosome.Furthermore,when an RNA ligand was employed,we showed that LACHT also enabled TPD of an RBP,Lin28a,leading to upregulation of its downstream let-7 miRNA.This study thus provides a generalizable platform to expand the TPD toolbox for biomedical applications.

GATA binding protein 2 mediated ankyrin repeat domain containing 26 high expression in myeloid-derived cell lines

BACKGROUND Thrombocytopenia 2,an autosomal dominant inherited disease characterized by moderate thrombocytopenia,predisposition to myeloid malignancies and normal platelet size and function,can be caused by 5’-untranslated region(UTR)point mutations in ankyrin repeat domain containing 26(ANKRD26).Runt related transcription factor 1(RUNX1)and friend leukemia integration 1(FLI1)have been identified as negative regulators of ANKRD26.However,the positive regulators of ANKRD26 are still unknown.AIM To prove the positive regulatory effect of GATA binding protein 2(GATA2)on ANKRD26 transcription.METHODS Human induced pluripotent stem cells derived from bone marrow(hiPSC-BM)INTRODUCTION Ankyrin repeat domain containing protein 26(ANKRD26)acts as a regulator of adipogenesis and is involved in the regulation of feeding behavior[1-3].The ANKRD26 gene is located on chromosome 10 and shares regions of homology with the primate-specific gene family POTE.According to the Human Protein Atlas database,the ANKRD26 protein is localized to the Golgi apparatus and vesicles,and its expression can be detected in nearly all human tissues[4].Moreover,UniProt annotation revealed that ANKRD26 is localized in the centrosome and contains coiled-coil domains formed by spectrin helices and ankyrin repeats[5,6].The most common disease related to ANKRD26 is thrombocytopenia 2(THC2),which is a rare autosomal dominant inherited disease characterized by lifelong mild-to-moderate thrombocytopenia and mild bleeding[7-9].Caused by the variants in the 5’-untranslated region(UTR)of ANKRD26,THC2 is defined by a decrease in the number of platelets in circulating blood and results in increased bleeding and decreased clotting ability[8,10].Due to the point mutations that occur in the 5’-UTR of ANKRD26,its negative transcription factors(TFs),Runt related transcription factor 1(RUNX1)and friend leukemia integration 1(FLI1),lose their repression effect[11].The persistent expression of ANKRD26 increases the activity of the mitogen activated protein kinase and extracellular signal regulated kinase 1/2 signaling pathways,which are potentially involved in the regulation of thrombopoietin-dependent signaling and further impair proplatelet formation by megakaryocytes(MKs)[11].However,the positive regulators of ANKRD26,which might be associated with THC2 pathology,are still unknown.

Fatty acid binding protein 5 is a novel therapeutic target for hepatocellular carcinoma

BACKGROUND Hepatocellular carcinoma(HCC)is an aggressive subtype of liver cancer and is one of the most common cancers with high mortality worldwide.Reprogrammed lipid metabolism plays crucial roles in HCC cancer cell survival,growth,and evolution.Emerging evidence suggests the importance of fatty acid binding proteins(FABPs)in contribution to cancer progression and metastasis;however,how these FABPs are dysregulated in cancer cells,especially in HCC,and the roles of FABPs in cancer progression have not been well defined.AIM To understand the genetic alterations and expression of FABPs and their associated cancer hallmarks and oncogenes in contributing to cancer malignancies.METHODS We used The Cancer Genome Atlas datasets of pan cancer and liver hepatocellular carcinoma(LIHC)as well as patient cohorts with other cancer types in this study.We investigated genetic alterations of FABPs in various cancer types.mRNA expression was used to determine if FABPs are abnormally expressed in tumor tissues compared to non-tumor controls and to investigate whether their expression correlates with patient clinical outcome,enriched cancer hallmarks and oncogenes previously reported for patients with HCC.We determined the protein levels of FABP5 and its correlated genes in two HCC cell lines and assessed the potential of FABP5 inhibition in treating HCC cells.RESULTS We discovered that a gene cluster including five FABP family members(FABP4,FABP5,FABP8,FABP9 and FABP12)is frequently co-amplified in cancer.Amplification,in fact,is the most common genetic alteration for FABPs,leading to overexpression of FABPs.FABP5 showed the greatest differential mRNA expression comparing tumor with non-tumor tissues.High FABP5 expression correlates well with worse patient outcomes(P<0.05).FABP5 expression highly correlates with enrichment of G2M checkpoint(r=0.33,P=1.1e-10),TP53 signaling pathway(r=0.22,P=1.7e-5)and many genes in the gene sets such as CDK1(r=0.56,P=0),CDK4(r=0.49,P=0),and TP53(r=0.22,P=1.6e-5).Furthermore,FABP5 also correlates well with two co-expressed oncogenes PLK1 and BIRC5 in pan cancer especially in LIHC patients(r=0.58,P=0;r=0.58,P=0;respectively).FABP5high Huh7 cells also expressed higher protein levels of p53,BIRC5,CDK1,CDK2,and CDK4 than FABP5low HepG2 cells.FABP5 inhibition more potently inhibited the tumor cell growth in Huh7 cells than in HepG2 cells.CONCLUSION We discovered that FABP5 gene is frequently amplified in cancer,especially in HCC,leading to its significant elevated expression in HCC.Its high expression correlates well with worse patient outcome,enriched cancer hallmarks and oncogenes in HCC.FABP5 inhibition impaired the cell viability of FABP5high Huh7 cells.All these support that FABP5 is a novel therapeutic target for treating FABP5high HCC.

Effect of glucocorticoid treatment on insulin like growth factor-Ⅰ and its binding proteins in children with nephrotic syndrome

Objective To identify the changes in serum insulin like growth factor Ⅰ (IGF Ⅰ) and IGF binding proteins (IGFBPs) in children with nephrotic syndrome (NS) and the effect of glucocorticoid on serum IGF Ⅰ and IGFBPs Methods We measured serum IGF Ⅰ and IGFBPs levels by radioimmune assay and immune radiomagnetic assay in 36 children with NS, consisting of an active stage group (ANS, n=12), a remission stage group (RE, n=12), an active stage group with glucocorticoid treatment (GNS, n=12), and a normal control group (NC, n=10) Results 1) Compared to NC, serum levels of IGF Ⅰ and IGFBP 3 were decreased ( P <0 01); serum levels of IGFBP 1 and IGFBP 2 were increased ( P <0 01) in the ANS group 2) Serum levels of IGF Ⅰ and IGFBP 3 were higher and IGFBP 1 and IGFBP 2 were lower in the RE Group than in theANS Group ( P <0 01) 3) Compared to the ANS group, serum levels of IGF Ⅰ and IGFBP 3 were increased ( P <0 01) and serum levels of IGFBP 1 and IGFBP 2 were decreased ( P <0 01) in the GNS group 4) A correlation was found between serum levels of IGFBP 3 and albumin in the active stage group ( r =0 76, P <0 01) There was also a correlation between serum levels of IGF Ⅰ and IGFBP 3 and an inverse correlation between the serum level of IGF Ⅰ and serum levels of IGFBP 1 and IGFBP 2 in the ANS group No other correlations were observed Conclusions The serum levels of IGF Ⅰ and IGFBPs are altered in children in the active stage of NS, but return to normal in the remission stage GC treatment may influence serum IGF Ⅰ and IGFBPs in children with NS Changes in IGF Ⅰ and IGFBPs levels may play a role in the growth retardation of NS children

Potential regulatory mechanism and clinical significance of synaptotagmin binding cytoplasmic RNA interacting protein in colorectal cancer

BACKGROUND Colorectal cancer(CRC)causes many deaths worldwide.Synaptotagmin binding cytoplasmic RNA interacting protein(SYNCRIP)is an RNA-binding protein that plays an important role in multiple cancers by epigenetically targeting some genes.Our study will examine the expression,potential effect,biological function and clinical value of SYNCRIP in CRC.AIM To examine the expression,potential effect,biological function and clinical value METHODS The expression of SYNCRIP was examined by immunohistochemistry arrays and high-throughput data.The effect of SYNCRIP gene in CRC cell growth was evaluated by CRISPR-Cas9 technology.The target genes of SYNCRIP were calculated using various algorithms,and the molecular mechanism of SYNCRIP in CRC was explored by mutation analysis and pathway analysis.The clinical value of SYNCRIP in prognosis and radiotherapy was revealed via evidence-based medicine methods.RESULTS The protein and mRNA levels of SYNCRIP were both highly expressed in CRC samples compared to nontumorous tissue based on 330 immunohistochemistry arrays and 3640 CRC samples.Cells grew more slowly in eleven CRC cell lines after knocking out the SYNCRIP gene.SYNCRIP could epigenetically target genes to promote the occurrence and development of CRC by boosting the cell cycle and affecting the tumor microenvironment.In addition,CRC patients with high SYNCRIP expression are more sensitive to radiotherapy.CONCLUSION SYNCRIP is upregulated in CRC,and highly expressed SYNCRIP can accelerate CRC cell division by exerting its epigenetic regulatory effects.In addition,SYNCRIP is expected to become a potential biomarker to predict the effect of radiotherapy.

Application of Cydia pomonella expressed sequence tags： Identification and expression of three general odorant binding proteins in codling moth

The codling moth, Cydia pomonella, is one of the most important pests of pome fruits in the world, yet the molecular genetics and the physiology of this insect remain poorly understood. A combined assembly of 8？341 expressed sequence tags was generated from Roche 454 GS-FLX sequencing of eight tissue-specific cDNA libraries. Putative chemosensory proteins （12） and odorant binding proteins （OBPs） （18） were annotated, which included three putative general OBP （GOBP）, one more than typically reported for other Lepidoptera. To further characterize CpomGOBPs, we cloned cDNA copies of their transcripts and determined their expression patterns in various tissues. Cloning and sequencing of the 698？nt transcript for CpomGOBP1 resulted in the prediction of a 163 amino acid coding region, and subsequent RT-PCR indicated that the transcripts were mainly expressed in antennae and mouthparts. The 1？289 nt （160 amino acid） CpomGOBP2 and the novel 702 nt （169 amino acid） CpomGOBP3 transcripts are mainly expressed in antennae, mouthparts, and female abdomen tips. These results indicate that next generation sequencing is useful for the identification of novel transcripts of interest, and that codling moth expresses a transcript encoding for a new member of the GOBP subfamily.

RNA binding proteins in spermatogenesis： an in depth focus on the Musashi family

Controlled gene regulation during gamete development is vital for maintaining reproductive potential. During the complex process of mammalian spermatogenesis, male germ cells experience extended periods of the inactive transcription despite heavy translational requirements for continued growth and differentiation. Hence, spermatogenesis is highly reliant on mechanisms of posttranscriptional regulation of gene expression, facilitated by RNA binding proteins （RBPs）, which remain abundantly expressed throughout this process. One such group of proteins is the Musashi family, previously identified as critical regulators of testis germ cell development and meiosis in Drosophila, and also shown to be vital to sperm development and reproductive potential in the mouse. This review describes the role and function of RBPs our recent knowledge of the Musashi proteins in spermatogenesis. within the scope of male germ cell development, focusing on The functional mechanisms utilized by RBPs within the cell are outlined in depth, and the significance of sub-cellular localization and stage-specific expression in relation to the mode and impact of posttranscriptional regulation is also highlighted. We emphasize the historical role of the Musashi family of RBPs in stem cell function and cell fate determination, as originally characterized in Drosophila and Xenopus, and conclude with our current understanding of the differential roles and functions of the mammalian Musashi proteins, Musashi-1 and Musashi-2, with a primary focus on our findings in spermatogenesis. This review highlights both the essential contribution of RBPs to posttranscriptional regulation and the importance of the Musashi family as master regulators of male gamete development.

Salt Dependent Association of Novel Mutants of TATA-Binding Proteins to DNA:Predictions from Theory and Experiments

The nonlinear Poisson-Boltzmann predictions of the salt-dependent association of proteins to DNA,SKpred,are fairly insensitive to the choice of atomic charges,radii,interior dielectric constant and treatment of the boundary between a biomolecule and the solvent.In this study we show that the SKpred is highly correlated with the conformational adaptability of the partners involved in the biomolecular binding process.This is demonstrated for the wild-type and mutant forms of the archaeon Pyrococcus woesi TATA-binding protein(PwTBP)in complex with DNA,on which we performed molecular mechanics energy minimizations with different protocols,and molecular dynamics simulations and then computed the SKpred on the resulting structures.It was found that the inter-molecular non bonded force field energy between the DNA and protein correlates linearly and significantly well with the SKpred.This correlation encompasses the wild-type and mutant variants of the PwTBP and provides us with a quick way to estimate the SKpred from a large ensemble of structures generated with Molecular Dynamics or Monte Carlo simulations.The corresponding experimental SKobs should also correlate with the inter-molecular non bonded force field energy between the protein and DNA,given that the underlying mechanisms in binding and salt-dependent effects are in fact the main contributors in the association of proteins/peptides to nucleic acids.We show that it is possible to fit experiments versus the inter-molecular non bonded force field energy between the protein and DNA,and use this relation to predict the SKobs in absolute numbers.Thus,we present two novel approaches to estimate both the SKpred and the SKobs for in silico modelled PwTBP novel mutants and even for TBPs from other organisms.This is a simple but powerful tool to suggest new experiments on the TBP-DNA type of macromolecular assemblies.We conclude by suggesting some mutants and a possible biological interpretation of how changes in solvent salinity affect the binding of proteins to DNA.

Insulin-like growth factor binding proteins 7 prevents dental pulp-derived mesenchymal stem cell senescence via metabolic downregulation of p21

Cellular senescence affects the efficacy of mesenchymal stem cells(MSCs)-mediated tissue regeneration.Insulin-like growth factor binding proteins-7(IGFBP7),as a member of the IGF family,is associated with osteogenic differentiation and the senescence of MSCs,but its exact function and mechanism remain unclear.We found IGFBP7 promoted the osteogenic differentiation and prevented the senescence of dental pulp-derived MSCs(DPSCs),as observed in the gain-of-function and lossof-function analyses,the senescence-associated marker p21 showed the most pronounced expression changes.We demonstrated that IGFBP7 activated the biological activity of SIRT1 deacetylase via metabolism,resulting in a deacetylation of H3K36ac and a decrease of the binding affinity of H3K36ac to p21 promoter,thereby reducing the transcription of p21,which ultimately prevents DPSCs senescence and promotes tissue regeneration.The activation of the mitochondrial electron transport chain(ETC)by Coenzyme Q10 could rescue the promotion of DPSC senescence induced by the knockdown of IGFBP7,whereas the inhibition of ETC by rotenone attenuated the prevention of DPSC senescence induced by IGFBP7 overexpression.In conclusion,our present results reveal a novel function of IGFBP7 in preventing DPSC senescence via the metabolism-induced deacetylation of H3K36ac and reduction of p21 transcription,suggesting that IGFBP7 is a potential target for promoting tissue regeneration in an aging environment.

Effects of different brush border membrane vesicle isolation protocols on proteomic analysis of Cry1Ac binding proteins from the midgut of Helicoverpa armigera

Brush border membrane vesicles （BBMV） isolated from insect midguts have been widely used to study CrylA binding proteins. Sample preparation is important in two- dimensional electrophoresis （2-DE）, so to determine a suitable BBMV preparation method in Helicoverpa armigera for 2-DE, we compared three published BBMV preparation methods mostly used in sodium dodecyl sulfate-polyacrylamide gel electrophoresis （SDS- PAGE）. All methods yielded similar types and numbers of binding proteins, but in different quantities. The Abdul-Rauf and Ellar protocol was the best of the three, but had limitations. Sufficient protein quantity is important for research involving limited numbers of insects, such as studies of insect resistance to Bacillus thuringiensis in the field. Consequently, we integrated the three BBMV isolation methods into a single protocol that yielded high quantities of BBMV proteins from H. armigera larval midguts, which proved suitable for 2- DE analysis.

Knockdown of polypyrimidine tract binding protein facilitates motor function recovery after spinal cord injury

After spinal cord injury(SCI),a fibroblast-and microglia-mediated fibrotic scar is formed in the lesion core,and a glial scar is formed around the fibrotic scar as a res ult of the activation and proliferation of astrocytes.Simultaneously,a large number of neuro ns are lost in the injured area.Regulating the dense glial scar and re plenishing neurons in the injured area are essential for SCI repair.Polypyrimidine tra ct binding protein(PTB),known as an RNA-binding protein,plays a key role in neurogenesis.Here,we utilized short hairpin RNAs(shRNAs)and antisense oligonucleotides(ASOs)to knock down PTB expression.We found that reactive spinal astrocytes from mice were directly reprogrammed into motoneuron-like cells by PTB downregulation in vitro.In a mouse model of compressioninduced SCI,adeno-associated viral shRNA-mediated PTB knockdown replenished motoneuron-like cells around the injured area.Basso Mouse Scale scores and forced swim,inclined plate,cold allodynia,and hot plate tests showed that PTB knockdown promoted motor function recovery in mice but did not improve sensory perception after SCI.Furthermore,ASO-mediated PTB knockdown improved motor function resto ration by not only replenishing motoneuron-like cells around the injured area but also by modestly reducing the density of the glial scar without disrupting its overall structure.Together,these findings suggest that PTB knockdown may be a promising therapeutic strategy to promote motor function recovery during spinal cord repair.

Fidgetin interacting with microtubule end binding protein EB3 affects axonal regrowth in spinal cord injury

Fidgetin,a microtubule-severing enzyme,regulates neurite outgrowth,axonal regeneration,and cell migration by trimming off the labile domain of microtubule polymers.Because maintenance of the microtubule labile domain is essential for axon initiation,elongation,and navigation,it is of interest to determine whether augmenting the microtubule labile domain via depletion of fidgetin serves as a therapeutic approach to promote axonal regrowth in spinal cord injury.In this study,we constructed rat models of spinal cord injury and sciatic nerve injury.Compared with spinal cord injury,we found that expression level of tyrosinated microtubules in the labile portion of microtubules continuously increased,whereas fidgetin decreased after peripheral nerve injury.Depletion of fidgetin enhanced axon regeneration after spinal cord injury,whereas expression level of end binding protein 3(EB3)markedly increased.Next,we performed RNA interference to knockdown EB3 or fidgetin.We found that deletion of EB3 did not change fidgetin expression.Conversely,deletion of fidgetin markedly increased expression of tyrosinated microtubules and EB3.Deletion of fidgetin increased the amount of EB3 at the end of neurites and thereby increased the level of tyrosinated microtubules.Finally,we deleted EB3 and overexpressed fidgetin.We found that fidgetin trimmed tyrosinated tubulins by interacting with EB3.When fidgetin was deleted,the labile portion of microtubules was elongated,and as a result the length of axons and number of axon branches were increased.These findings suggest that fidgetin can be used as a novel therapeutic target to promote axonal regeneration after spinal cord injury.Furthermore,they reveal an innovative mechanism by which fidgetin preferentially severs labile microtubules.

Large-scale analysis of the position-dependent binding and regulation of human RNA binding proteins

Background:RNA binding proteins(RBPs)play essential roles in the regulation of RNA metabolism.Recent studies have disclosed that RBPs achieve their functions via binding to their targets in a position-dependent pattern on RNAs.However,few studies have systematially addressed the associations between the RBP's functions and their positional binding preferences.Methods:Here,we present large-scale analyses on the functional targets of human RBPs by integrating the enhanced cross-linking and immunoprecipitation followed by sequencing(eCLIP-seq)datasets and the shRNA knockdown followed by RNA-seq datasets that are deposited in the integrated ENCyclopedia of DNA Elements in the human genome(ENCODE)data portal.Results:We found that(1)binding to the translation termination site and the 3'untranslated region is important to most human RBP's in the RNA decay regulation;(2)RBPs’binding and regulation follow a cell-ty pe specific pattern.Conclusions:These analysis results show the strong relationship between the binding position and the functions of RBPs,which provides novel insights into the RBPs'regulation mechanisms.