Ubiquitin, TAK1 and IKK: is there a connection?
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Animals↗
Biomedical subjects
Z J Chen
Publications and source records attributed to Z J Chen.
Molecular marker genotypes, heterozygosity and genetic interactions explain heterosis in Arabidopsis thaliana.
The underlying mechanisms for hybrid vigor or heterosis are elusive. Here we report a population of recombinant inbred lines (RILs), derived from the two ecotypes, Col and Ler, which can serve as a permanent resource for studying the molecular basis of hybrid vigor in Arabidopsis. Using a North Carolina mating design III (NCIII), we determined the additive and dominant nature of gene action in this population. We detected heterosis among crosses of RILs with one of the two parents (Col and Ler) and analyzed genotypes and heterozygosities for RILs and test cross families (RILs crossed to Col and Ler) using a total of 446 published molecular markers. The performance of RILs and additive and dominant components in the test cross families were used to analyze QTLs for 16 traits, using QTL cartographer and composite interval mapping with 1,000 permutations for each trait. Our data suggest that locus-specific and/or genome-wide differential heterozygosity, including epistasis, plays an important role in the generation of the observed heterosis. Furthermore, the hybrid vigor occurred between two closely related ecotypes, and provides a general mechanism for novel variation generated between genetically similar materials.
Arabidopsis↗
Gene symbol: MSH2. Disease: Hereditary nonpolyposis colorectal cancer.
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Amino Acid Substitution↗
Effects of sucrose concentration on the developmental potential of human frozen-thawed oocytes at different stages of maturity.
BACKGROUND: Success of human oocyte cryopreservation depends on multiple cryobiological factors that could influence the developmental potential of the oocytes. The objective of this study was to examine the effects of different sucrose concentrations on the developmental potential of human frozen-thawed oocytes at different maturity stages. METHODS: A total of 355 oocytes collected from small follicles were randomly divided into three groups and two groups (B and C) were cryopreserved using slow-freezing method. Group A included 131 oocytes at different maturity stages without freezing. Another 119 oocytes in Group B were cryopreserved with 0.1 M sucrose and 105 oocytes in Group C with 0.2 M sucrose concentration. RESULTS: The post-thaw survival rate of the oocytes and the cleavage rate in Group C were significantly higher than that of Group B (P<0.05). For immature metaphase I (MI) stage oocytes, a significant difference was found in the maturation rate between Group C and Group B (P<0.05). The maturation rate for the GV oocytes in Groups A and C was significantly higher than Group B (P<0.01). CONCLUSIONS: The results suggested that sucrose concentration of 0.2 M in the cryoprotectant solution is more suitable for human oocyte cryopreservation.
Adult↗
Rupture of pregnancy in a communicating rudimentary uterine horn after in vitro fertilization and embryo transfer.
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Adult↗
Genetic mapping and QTL analysis of fiber-related traits in cotton ( Gossypium).
Cotton, the leading natural fiber crop, is largely produced by two primary cultivated allotetraploid species known as Upland or American cotton ( Gossypium hirsutum L.) and Pima or Egyptian cotton ( G. barbadense L.). The allotetraploid species diverged from each other and from their diploid progenitors (A or D genome) through selection and domestication after polyploidization. To analyze cotton AD genomes and dissect agronomic traits, we have developed a genetic map in an F2 population derived from interspecific hybrids between G. hirsutum L. cv. Acala-44 and G. barbadense L. cv. Pima S-7. A total of 392 genetic loci, including 333 amplified fragment length polymorphisms (AFLPs), 47 simple sequence repeats (SSRs), and 12 restriction fragment length polymorphisms (RFLPs), were mapped in 42 linkage groups, which span 3,287 cM and cover approximately 70% of the genome. Using chromosomal aneuploid interspecific hybrids and a set of 29 RFLP and SSR framework markers, we assigned 19 linkage groups involving 223 loci to 12 chromosomes. Comparing four pairs of homoeologous chromosomes, we found that with one exception linkage distances in the A-subgenome chromosomes were larger than those in their D-subgenome homoeologues, reflecting higher recombination frequencies and/or larger chromosomes in the A subgenome. Segregation distortion was observed in 30 out of 392 loci mapped in cotton. Moreover, approximately 29% of the RFLPs behaved as dominant loci, which may result from rapid genomic changes. The cotton genetic map was used for quantitative trait loci (QTL) analysis using composite interval mapping and permutation tests. We detected seven QTLs for six fiber-related traits; five of these were distributed among A-subgenome chromosomes, the genome donor of fiber traits. The detection of QTLs in both the A subgenome in this study and the D subgenome in a previous study suggests that fiber-related traits are controlled by the genes in homoeologous genomes, which are subjected to selection and domestication. Some chromosomes contain clusters of QTLs and presumably contribute to the large amount of phenotypic variation that is present for fiber-related traits.
Chromosome Mapping↗
Deposition of the NG2 proteoglycan at nodes of Ranvier in the peripheral nervous system.
The node of Ranvier is a complex macromolecular assembly of ion channels and other proteins that is specialized for the rapid propagation of the action potential. A full understanding of the processes responsible for the assembly and maintenance of the node requires first the identification and characterization of the proteins found there. Here we show that NG2, a structurally unique chondroitin sulfate proteoglycan, is a molecular component of the node of Ranvier in the peripheral nervous system. In adult sciatic nerve, NG2 is (1) associated with thin, elongated fibroblast-like cells, (2) on some but not all basal laminae, and (3) at nodes of Ranvier. At the nodes, NG2 is restricted to the nodal gap and is absent from the paranodal or juxtaparanodal region. In dissociated cell cultures of adult sciatic nerve, perineurial fibroblasts but not Schwann cells express NG2 on their surfaces. Approximately 45% of the total NG2 in peripheral nerves is in a soluble, rather than particulate, subcellular compartment. NG2 is also present in membrane fractions that also contain high levels of voltage-dependent sodium channels, caspr, and neuron-glia related cell adhesion molecule. These medium-density membranes likely correspond to the nodal and paranodal region of the axon-Schwann cell unit. These results suggest a model in which perineurial fibroblasts secrete or shed NG2, which subsequently associates with nodes of Ranvier. The growth-inhibitory and anti-adhesive properties of NG2 may limit the lateral extension of myelinating Schwann cells as nodes mature. NG2 may also participate in the barrier functions of the perineurial linings of the nerve.
Animals↗
TAK1 is a ubiquitin-dependent kinase of MKK and IKK.
TRAF6 is a signal transducer that activates IkappaB kinase (IKK) and Jun amino-terminal kinase (JNK) in response to pro-inflammatory mediators such as interleukin-1 (IL-1) and lipopolysaccharides (LPS). IKK activation by TRAF6 requires two intermediary factors, TRAF6-regulated IKK activator 1 (TRIKA1) and TRIKA2 (ref. 5). TRIKA1 is a dimeric ubiquitin-conjugating enzyme complex composed of Ubc13 and Uev1A (or the functionally equivalent Mms2). This Ubc complex, together with TRAF6, catalyses the formation of a Lys 63 (K63)-linked polyubiquitin chain that mediates IKK activation through a unique proteasome-independent mechanism. Here we report the purification and identification of TRIKA2, which is composed of TAK1, TAB1 and TAB2, a protein kinase complex previously implicated in IKK activation through an unknown mechanism. We find that the TAK1 kinase complex phosphorylates and activates IKK in a manner that depends on TRAF6 and Ubc13-Uev1A. Moreover, the activity of TAK1 to phosphorylate MKK6, which activates the JNK-p38 kinase pathway, is directly regulated by K63-linked polyubiquitination. We also provide evidence that TRAF6 is conjugated by the K63 polyubiquitin chains. These results indicate that ubiquitination has an important regulatory role in stress response pathways, including those of IKK and JNK.
Adaptor Proteins, Signal Transducing↗
Protein-coding genes are epigenetically regulated in Arabidopsis polyploids.
The fate of redundant genes resulting from genome duplication is poorly understood. Previous studies indicated that ribosomal RNA genes from one parental origin are epigenetically silenced during interspecific hybridization or polyploidization. Regulatory mechanisms for protein-coding genes in polyploid genomes are unknown, partly because of difficulty in studying expression patterns of homologous genes. Here we apply amplified fragment length polymorphism (AFLP)-cDNA display to perform a genome-wide screen for orthologous genes silenced in Arabidopsis suecica, an allotetraploid derived from Arabidopsis thaliana and Cardaminopsis arenosa. We identified ten genes that are silenced from either A. thaliana or C. arenosa origin in A. suecica and located in four of the five A. thaliana chromosomes. These genes represent a variety of RNA and predicted proteins including four transcription factors such as TCP3. The silenced genes in the vicinity of TCP3 are hypermethylated and reactivated by blocking DNA methylation, suggesting epigenetic regulation is involved in the expression of orthologous genes in polyploid genomes. Compared with classic genetic mutations, epigenetic regulation may be advantageous for selection and adaptation of polyploid species during evolution and development.
Arabidopsis↗
Gene expression profiling using a novel method: amplified differential gene expression (ADGE).
Amplified differential gene expression (ADGE) is a novel technique, designed to profile gene expression of the whole transcriptome or to compare expression of a set of genes between two samples. ADGE employs hybridization to quadratically amplify the ratio of an expressed gene between control and tester samples before displaying. The subtle structures of adapters and primers are designed for displaying the amplified ratio of an expressed gene between two samples. Four selective nucleotides at the 3' end of primers are used to increase PCR efficiency for targeted molecules and to improve detection of PCR products. Double PCR with the same pair of primers expands the detection range, especially for genes of low abundance. Integration of these steps makes ADGE sensitive and accurate. Application to drug resistant human tumor cell lines showed that ADGE accurately profiled expression levels for induced, repressed or unchanged genes. The qualitative expression patterns for ADGE were verified with RT-PCR.
DNA Primers↗
Proteolytic activation of membrane-bound guanylate cyclase.
Membrane-bound guanylate cyclase-A (GC-A), the receptor for atrial natriuretic factor (ANF), has been shown to be regulated by its kinase-like domain. To resolve the nature of this regulation, we measured the effects of various proteases on the activity of guanylate cyclase in rat lung membranes, and on the activity of the bacterial-expressed catalytic domain (GC-c) and on a recombinant peptide composed of both the kinase-like and catalytic domain (GC-kc) of guanylate cyclase. Pronase increased rat guanylate cyclase activity in a biphasic manner with a maximal effect at about 10-20 microg per assay tube. Thermolysin had effects similar to those of pronase on the activity of guanylate cyclase in rat lung membranes. In the case of bacterial-expressed proteins, pronase increased the activity of GC-kc, but not GC-c. These results indicate that GC-A contains an autoinhibitory site on its kinase-like domain, and that removal of the autoinhibitory site by limited proteolysis leads to enzyme activation. GC-A was poorly activated by ANF and ATP after the rat lung membrane was pretreated with pronase, suggesting that ANF/ATP and pronase activate guanylate cyclase through the same mechanism. It is suggested that the binding of ANF and ATP to GC-A may induce a conformational change of the receptor that releases the inhibitory constraint on enzyme activity leading to enzyme activation.
Adenosine Triphosphate↗
Blocking histone deacetylation in Arabidopsis induces pleiotropic effects on plant gene regulation and development.
Histone acetylation and deacetylation play essential roles in eukaryotic gene regulation. Reversible modifications of core histones are catalyzed by two intrinsic enzymes, histone acetyltransferase and histone deacetylase (HD). In general, histone deacetylation is related to transcriptional gene silencing, whereas acetylation correlates with gene activation. We produced transgenic plants expressing the antisense Arabidopsis HD (AtHD1) gene. AtHD1 is a homolog of human HD1 and RPD3 global transcriptional regulator in yeast. Expression of the antisense AtHD1 caused dramatic reduction in endogenous AtHD1 transcription, resulting in accumulation of acetylated histones, notably tetraacetylated H4. Reduction in AtHD1 expression and AtHD1 production and changes in acetylation profiles were associated with various developmental abnormalities, including early senescence, ectopic expression of silenced genes, suppression of apical dominance, homeotic changes, heterochronic shift toward juvenility, flower defects, and male and female sterility. Some of the phenotypes could be attributed to ectopic expression of tissue-specific genes (e.g., SUPERMAN) in vegetative tissues. No changes in genomic DNA methylation were detected in the transgenic plants. These results suggest that AtHD1 is a global regulator, which controls gene expression during development through DNA-sequence independent or epigenetic mechanisms in plants. In addition to DNA methylation, histone modifications may be involved in a general regulatory mechanism responsible for plant plasticity and variation in nature.
Acetylation↗
Characterization of murine polyreactive antigen-binding B cells: presentation of antigens to T cells.
Monoclonal polyreactive antibodies (Ab) can bind, at low affinity, a variety of different self and non-self antigens (Ag). Recent studies in humans showed that polyreactive Ab are expressed on the surface of a subset of peripheral B lymphocytes and clonal analysis revealed that a variety of different Ag can bind to single cells expressing these Ab. To see if these polyreactive Ag-binding B (PAB) cells also are present in mice, fluorescein-conjugated Ag and FACS sorting were used to identify and separate PAB cells from non-polyreactive Ag-binding B cells. Depending on the Ag used for screening, up to one-third of mouse splenic B cells displayed polyreactive Ag-binding properties. Confirmation that the Ag actually bound to surface Ig came from treating PAB cells with anti-Ig which inhibited Ag binding by up to 80 %. Further studies showed that PAB cells could present Ag to Ag-specific T cells, but despite their Ag-presenting ability, PAB cells from normal mice failed to trigger Ag-specific T cells to proliferate. Analysis of the co-stimulatory molecules B7-1 and B7-2 showed that these molecules were not expressed on PAB cells from normal mice. These findings argue that the lack of co-stimulatory molecules on PAB cells is the most likely explanation for their failure to stimulate Ag-specific T cells. The ability of PAB cells from normal mice to bind and present Ag to Ag-specific T cells, without causing them to proliferate, suggests that PAB cells may contribute to the induction and / or maintenance of immunological tolerance.
Animals↗
17beta-estradiol inhibits soluble guanylate cyclase activity through a protein tyrosine phosphatase in PC12 cells.
Besides its involvement in reproductive functions, estrogen protects against the development of cardiovascular diseases. The guanylate cyclase/cGMP system is known to exert potent effects on the regulation of blood pressure and electrolyte balance. We examined whether 17beta-estradiol can affect soluble guanylate cyclase in PC12 cells. The results indicate that 17beta-estradiol decreases cGMP levels in PC12 cells. 17beta-Estradiol decreases sodium nitroprusside (SNP)-stimulated, but not atrial natriuretic factor-stimulated cGMP formation in PC12 cells, indicating that 17beta-estradiol decreases cGMP levels by inhibiting the activity of soluble guanylate cyclase. 17beta-Estradiol also stimulates protein tyrosine phosphatase activities in PC12 cells and dephosphorylates at least three proteins. Addition of sodium vanadate, a protein tyrosine phosphatase inhibitor, blocks the inhibitory effects of 17beta-estradiol on soluble guanylate cyclase activity in PC12 cells. Furthermore, transfection of SHP-1, a protein tyrosine phosphatase, into PC12 cells inhibits both basal and SNP-stimulated guanylate cyclase activity. Amino acid analysis also reveals that the 70-kDa subunit of soluble guanylate cyclase contains the SHP-1 substrate consensus sequence. These results suggest that 17beta-estradiol inhibits soluble guanylate cyclase activity through SHP-1.
Animals↗
Overexpression of cardiac I-kappaBalpha prevents endotoxin-induced myocardial dysfunction.
Nuclear factor-kappa B (NF-kappaB) is an inducible transcription factor that regulates expression of many genes, such as tumor necrosis factor-alpha (TNF-alpha), which may contribute to myocardial dysfunction. We investigated whether cardiac NF-kappaB activation is involved in the development of myocardial dysfunction after lipopolysaccharide (LPS) challenge. Mice were intraperitoneally injected with LPS, and the hearts were harvested and assayed for NF-kappaB translocation. After LPS challenge, NF-kappaB activation was detected within 30 min and remained for 8 h. In transgenic mice constitutively overexpressing a nondegradable form of I-kappaBalpha (I-kappaBalphaDeltaN) in cardiomyocytes, myocardial NF-kappaB translocation was prevented after LPS challenge. Myocytes isolated from these transgenics secreted significantly less TNF-alpha than did wild-type cardiomyocytes after LPS stimulation. When whole hearts were excised, perfused in a Langendorff preparation, and challenged with endotoxin, I-kappaBalphaDeltaN transgenic hearts displayed normal cardiac function, whereas profound contractile dysfunction was observed in wild-type hearts. These data indicate that myocardial NF-kappaB translocates within minutes after LPS administration. Inhibition of myocyte NF-kappaB activation by overexpression of myocyte I-kappaBalpha is sufficient to block cardiac TNF-alpha production and prevent cardiac dysfunction after LPS challenge.
Animals↗
Antioxidants, vitamin C and dithiothreitol, activate membrane-bound guanylate cyclase in PC12 cells.
Antioxidants and antioxidant enzymes are known to protect against cell death induced by reactive oxygen species. However, apart from directly quenching free radicals, little is known about the effect of antioxidants on hormone-activated second messenger systems. We previously found that antioxidants such as 17-beta estradiol and resveratrol activate membrane-bound guanylate cyclase GC-A, the receptor for atrial natriuretic factor (ANF), in PC12 cells. It is possible that other antioxidants may also activate membrane-bound guanylate cyclase GC-A. The aim of this study was to determine if dithiothreitol (DTT), vitamin C, and vitamin E activate membrane-bound guanylate cyclase GC-A in PC12 cells. The results showed that both DTT and vitamin C increased cGMP levels in PC12 cells, whereas vitamin E had no effect. DTT and vitamin C inhibited membrane-bound guanylate cyclase activity stimulated by ANF in PC12 cells. In contrast, DTT and vitamin C had no effect on soluble guanylate cyclase activity stimulated by substance P. Furthermore, NO synthase inhibitors L-NAME and aminoguanidine did not affect DTT- and vitamin C-stimulated guanylate cyclase activity. The results indicate that DTT and vitamin C, but not vitamin E, activate membrane-bound guanylate cyclase GC-A in PC12 cells.
Animals↗
Binding of the aminothiol WR-1065 to transcription factors influences cellular response to anticancer drugs.
The aminothiol WR-1065 (the active form of amifostine) protects normal tissues from the toxic effects of certain cancer drugs, while leaving their antitumor effects unchanged. The present data address the mechanism of action of this dichotomous effect. (35)S-Labeled WR-1065 bound directly to the transcription factors nuclear factor-kappaB, activator protein-1, and p53, resulting in enhanced binding of these proteins to target regulatory DNA sequences and subsequent transactivation of a number of downstream genes. Since other small molecular thiols could mimic WR-1065, the redox potential of the sulfhydryl is an important determinant of its activity. In nontransformed cells, WR-1065 protected cells from the cytotoxic effects of paclitaxel in a p53-dependent manner. However, in a transformed human tumor cell line, there was no cytoprotectivity by WR-1065, consistent with the premise that p53-dependent growth arrest is the basis for the protective effect of this compound, and that this pathway is abrogated in human tumors. The combined data support the principle that the cellular effects of the aminothiol WR-1065 are mediated through an impact on transcriptional regulation and are not only a consequence of radical scavenging.
Animals↗
[Studies on saponin accumulative in regularities Panax notoginseng (Burk) F. H. Chen].
OBJECTIVE: To determine the optimal harvest time for P. notoginseng through studying the changes of saponin contents with growth periods. METHODS: P. notoginseng samples were collected from the experimental plot regularly, and then the contents of total saponin and some main single saponins were analyzed by HPLC. RESULTS: Total saponin contents decreased from April through July, and increased from August through December. CONCLUSION: The optimal harvest time is determined as from October through December, which corresponds to the traditional harvest time.
Ginsenosides↗