Biomedical subjects

Wen-Hui Shen

Publications and source records attributed to Wen-Hui Shen.

17 recordsLinked to original sources

PubMed2006

Arabidopsis NRP1 and NRP2 encode histone chaperones and are required for maintaining postembryonic root growth.

NUCLEOSOME ASSEMBLY PROTEIN1 (NAP1) is conserved from yeast to human and was proposed to act as a histone chaperone. While budding yeast contains a single NAP1 gene, multicellular organisms, including plants and animals, contain several NAP1 and NAP1-RELATED PROTEIN (NRP) genes. However, the biological role of these genes has been largely unexamined. Here, we show that, in Arabidopsis thaliana, simultaneous knockout of the two NRP genes, NRP1 and NRP2, impaired postembryonic root growth. In the nrp1-1 nrp2-1 double mutant, arrest of cell cycle progression at G2/M and disordered cellular organization occurred in root tips. The mutant seedlings exhibit perturbed expression of approximately 100 genes, including some genes involved in root proliferation and patterning. The mutant plants are highly sensitive to genotoxic stress and show increased levels of DNA damage and the release of transcriptional gene silencing. NRP1 and NRP2 are localized in the nucleus and can form homomeric and heteromeric protein complexes. Both proteins specifically bind histones H2A and H2B and associate with chromatin in vivo. We propose that NRP1 and NRP2 act as H2A/H2B chaperones in the maintenance of dynamic chromatin in epigenetic inheritance.

Arabidopsis↗

PubMed2005

Prevention of early flowering by expression of FLOWERING LOCUS C requires methylation of histone H3 K36.

Flowering represents a crucial transition from a vegetative to a reproductive phase of the plant life cycle. Despite extensive studies, the molecular mechanisms controlling flowering remain elusive. Although the enzymes involved are unknown, methylation of histone H3 K9 and K27 correlates with repression of FLOWERING LOCUS C (FLC), an essential transcriptional repressor involved in flowering time control in Arabidopsis thaliana; in contrast, methylation of H3K4 correlates with FLC activation. Here we show that loss-of-function of SET DOMAIN GROUP 8 (SDG 8), which encodes a homologue of the yeast SET2 histone methyltransferase, results in reduced dimethylation of histone H3K36, particularly in chromatin associated with the FLC promoter and the first intron, regions that contain essential cis-elements for transcription. sdg8 mutants display reduced FLC expression and flower early, establishing SDG8-mediated H3K36 methylation as a novel epigenetic memory code required for FLC expression in preventing early flowering. This is the first demonstrated role of H3K36 methylation in eukaryote development.

Arabidopsis↗

PubMed2005

Interacting proteins and differences in nuclear transport reveal specific functions for the NAP1 family proteins in plants.

Nucleosome assembly protein 1 (NAP1) is conserved from yeast to human and facilitates the in vitro assembly of nucleosomes as a histone chaperone. Inconsistent with their proposed function in the nucleus, however, many NAP1 proteins had been reported to localize in the cytoplasm. We investigated the subcellular localization of tobacco (Nicotiana tabacum) and rice (Oryza sativa) NAP1 family proteins first by identification of interacting partners and by direct examination of the localization of green fluorescent protein-tagged proteins. Through treatment of tobacco cells with leptomycin B and mutagenesis of nuclear export signal, we demonstrated that Nicta;NAP1;1 and Orysa;NAP1;1 shuttle between the cytoplasm and the nucleus. Together with the demonstration that tobacco NAP1 proteins bind histone H2A and H2B, our results support the current model and provide additional evidence that function of NAP1 as histone chaperones appears to be conserved in plants. In addition, we show that tobacco NAP1 proteins interact with tubulin and the mitotic cyclin Nicta;CYCB1;1, suggesting a role for NAP1 in microtubule dynamics. Interestingly, in spite of their high homology with the above NAP1 proteins, the other three tobacco proteins and Orysa;NAP1;2 did not show nucleocytoplasmic shuttling and were localized only in the cytoplasm. Moreover, Orysa;NAP1;3 that lacks a typical nuclear localization signal sequence was localized in both the cytoplasm and the nucleus. Finally, we show that only Orysa;NAP1;3 could be phosphorylated by casein kinase 2alpha in vitro. However, this phosphorylation was not responsible for nuclear import of Orysa;NAP1;3 as being demonstrated through mutagenesis studies. Together, our results provide an important step toward elucidating the molecular mechanism of function of the NAP1 family proteins in plants.

Active Transport, Cell Nucleus↗

PubMed2005

Molecular and functional characterization of Arabidopsis Cullin 3A.

Cullin proteins, which belong to multigenic families in all eukaryotes, associate with other proteins to form ubiquitin protein ligases (E3s) that target substrates for proteolysis by the 26S proteasome. Here, we present the molecular and genetic characterization of a plant Cullin3. In contrast to fungi and animals, the genome of the model plant Arabidopsis thaliana contains two related CUL3 genes, called CUL3A and CUL3B. We found that CUL3A is ubiquitously expressed in plants and is able to interact with the ring-finger protein RBX1. A genomic search revealed the existence of at least 76 BTB-domain proteins in Arabidopsis belonging to 11 major families. Yeast two-hybrid experiments indicate that representative members of certain families are able to physically interact with both CUL3A and CUL3B, suggesting that Arabidopsis CUL3 forms E3 protein complexes with certain BTB domain proteins. In order to determine the function of CUL3A, we used a reverse genetic approach. The cul3a null mutant flowers slightly later than the control plants. Furthermore, this mutant exhibits a reduced sensitivity of the inhibition of hypocotyl growth in far-red light and miss-expresses COP1. The viability of the mutant plants suggests functional redundancy between the two CUL3 genes in Arabidopsis.

Arabidopsis↗

PubMed2004

Ectopic expression of the NtSET1 histone methyltransferase inhibits cell expansion, and affects cell division and differentiation in tobacco plants.

The tobacco NtSET1 gene encodes a member of the SUV39H family of histone methyltransferases. Ectopic expression of NtSET1 causes an increase in methylated histone H3 lysine 9 and abnormal chromosome segregation in tobacco suspension cells, and inhibits tobacco plant growth. Here we show that the inhibition of plant growth was caused by reduced cell expansion as well as by abnormal cell division and differentiation. We found that deletion of the C-terminally located catalytic domain of the protein abolished the ectopic effects of NtSET1 on plant growth. Our results indicate that histone H3 lysine 9 methylation is a critical mark of epigenetic control for plant development.

Cell Differentiation↗

PubMed2004

Molecular characterization of the tobacco SET domain protein NtSET1 unravels its role in histone methylation, chromatin binding, and segregation.

Plants contain a great number of genes encoding a distinctive class of SET domain proteins which harbor a plant-specific N-terminal part together with a C-terminal part showing highest sequence similarity to the catalytic domain of the yeast CLR4, the human SUV39H1 and G9a histone-methyltransferases (HMTases). Here we show that NtSET1, a representative member of this class from tobacco, methylated both K9 and K27 of histone H3 in vitro. Ectopic expression of NtSET1, by an inducible promoter, increased the amount of dimethylated H3K9 and induced chromosome-segregation defects in tobacco BY2 cells. Deletion analyses show that the HMTase activity, the association with specific chromatin regions and with condensed chromosomes, and the cellular effects largely depended on the C-terminal region including the SET domain of the protein. Nevertheless, the N-terminal part of NtSET1 was capable of targeting the green fluorescent protein to interphase chromatin. Finally, we show that NtSET1 bound LHP1, the Arabidopsis homolog of animal heterochromatin protein 1 (HP1), and that LHP1 co-localized with heterochromatin containing high amounts of dimethylated H3K9, suggesting a role for NtSET1 in heterochromatic function. Taken together, our results provide new insights into the molecular and global chromatin-binding activities of this particular class member of plant SET domain proteins.

Amino Acid Sequence↗

PubMed2004

Plants contain a high number of proteins showing sequence similarity to the animal SUV39H family of histone methyltransferases.

The SET domain, first identified within and named after proteins encoded by three Drosophila genes [Su(var)3-9, E(z), and Trithorax], is recognized as a signature motif for histone methyltransferases that are involved in epigenetic processes. The SUV39H family of SET domain proteins methylate specifically the residue lysine 9 of histone H3, creating a code for gene silencing. This family of proteins contain at their C termini a unique catalytic domain consisting of pre-SET, SET, and post-SET domains. Sequence homology-based searches identified 15 Arabidopsis, 14 maize, and 12 rice proteins that can be assigned to the SUV39H family. These high numbers in plants are in marked contrast to the situation in animals, in which each species appears to contain only two to three proteins of this family. Our phylogenetic analyses revealed that plant proteins can be classified into seven orthology groups. Representative members of each group can be found in single plant species, suggesting that different group members are evolutionarily conserved to perform specific functions.

Animals↗

PubMed2003

The tobacco A-type cyclin, Nicta;CYCA3;2, at the nexus of cell division and differentiation.

Although most of the components of the cell cycle machinery are conserved in all eukaryotes, plants differ strikingly from animals by the absence of a homolog of E-type cyclin, an important regulator involved in G1/S-checkpoint control in animals. By contrast, plants contain a complex range of A-type cyclins, with no fewer than 10 members in Arabidopsis. We previously identified the tobacco A-type cyclin Nicta;CYCA3;2 as an early G1/S-activated gene. Here, we show that antisense expression of Nicta;CYCA3;2 in tobacco plants induces defects in embryo formation and impairs callus formation from leaf explants. The green fluorescent protein (GFP)-Nicta;CYCA3;2 fusion protein was localized in the nucleoplasm. Transgenic tobacco plants overproducing GFP-Nicta;CYCA3;2 could not be regenerated from leaf disc transformation, whereas some transgenic Arabidopsis plants were obtained by the floral-dip transformation method. Arabidopsis plants that overproduce GFP-Nicta;CYCA3;2 showed reduced cell differentiation and endoreplication and a dramatically modified morphology. Calli regenerated from leaf explants of these transgenic Arabidopsis plants were defective in shoot and root regeneration. We propose that Nicta;CYCA3;2 has important functions, analogous to those of cyclin E in animals, in the control of plant cell division and differentiation.

Antisense Elements (Genetics)↗

PubMed2003

Comparison of bronchodilating and antiinflammatory activities of oral formoterol and its (R,R)-enantiomers.

AIM: To compare the bronchodilating and antiinflammatory effects of oral racemic formoterol (rac-FMT) and (R,R)-formoterol (R,R-FMT). METHODS: The changes of lung resistance (RL), dynamic lung compliance (Cdyn), and the accumulation of inflammatory cells in bronchoalveolar lavage fluids (BALF) induced by ovalbumin aerosol in sensitized guinea pigs and mice were investigated in vivo. RESULTS: Mean value increase of RL and mean value reduction of Cdyn from 1 to 30 min after antigen challenge were up to 101 %+/-34 % and 42 %+/-7 %, respectively. rac-FMT 0.5, 1.0, and 2.0 mg/kg, and R,R-FMT 0.25, 0.5, and 1.0 mg/kg ig, induced dose-related inhibition of the bronchoconstrictive responses to aerosolised ovalbumin. ID50 (95% confidence limits, 95 % CL) value of rac-FMT on RL maximal increase and Cdyn maximal reduction at 5 min were 0.64 (0.54-0.76) and 1.02 (0.88-1.18) mg/kg, respectively. For R,R-FMT they were 0.46 (0.40-0.53) and 0.52 (0.45-0.61) mg/kg, respectively. ID50 (95 % CL) value of rac-FMT on RL mean increase and Cdyn mean reduction from 1 to 30 min were 0.96 (0.86-1.07) and 1.59 (1.32-1.92) mg/kg, respectively. For R,R-FMT they were 0.52 (0.45-0.59) and 0.43 (0.37-0.51) mg/kg, respectively. Ovalbumin-aerosol challenge induced an increase of inflammatory cells in BALF in sensitized mice. rac-FMT and RR-FMT caused a dose-dependent and almost complete inhibition at 2.0 mg/kg. ID50 (95 % CL) of rac-FMT on the number of total inflammatory cells and eosinophil in BALF were 1.48 (1.22-1.81) and 0.80 (0.62-1.04) mg/kg, respectively. ID50 (95 % CL) of RR-FMT were 0.80 (0.57-1.13) and 0.60 (0.43-0.83) mg/kg, respectively. CONCLUSION: R,R-FMT protected lung against increase of RL and reduction of Cdyn induced by bronchial challenge of ovalbumin in the asthma model of guinea pigs, and inhibited airway inflammation in the sensitized mice. Efficacy of R,R-FMT was approximately 2-fold than that of rac-FMT.

Airway Resistance↗

PubMed2002

The AtRbx1 protein is part of plant SCF complexes, and its down-regulation causes severe growth and developmental defects.

Recently in yeast and animal cells, one particular class of ubiquitin ligase (E3), called the SCF, was demonstrated to regulate diverse processes including cell cycle and development. In plants SCF-dependent proteolysis is also involved in different developmental and hormonal regulations. To further investigate the function of SCF, we characterized at the molecular level the Arabidopsis RING-H2 finger protein AtRbx1. We demonstrated that the plant gene is able to functionally complement a yeast knockout mutant strain and showed that AtRbx1 protein interacts physically with at least two members of the Arabidopsis cullin family (AtCul1 and AtCul4). AtRbx1 also associates with AtCul1 and the Arabidopsis SKP1-related proteins in planta, indicating that it is part of plant SCF complexes. AtRbx1 mRNAs accumulate in various tissues of the plant, but at higher levels in tissues containing actively dividing cells. Finally to study the function of the gene in planta, we either overexpressed AtRbx1 or reduced its expression by a dsRNA strategy. Down-regulation of AtRbx1 impaired seedling growth and development, indicating that the gene is essential in plants. Furthermore, the AtRbx1-silenced plants showed a reduced level of AtCul1 protein, but accumulated higher level of cyclin D3.

Amino Acid Sequence↗

PubMed2002

Regulation of biosynthesis and intracellular localization of rice and tobacco homologues of nucleosome assembly protein 1.

The nucleosome assembly protein 1 (NAP1) is considered to be a conserved histone chaperone, facilitating the assembly of nucleosomes in all eukaryotes. However, studies in yeast and animal cells also indicated that NAP1 proteins have diverse functions likely independent of nucleosome-assembly activity. Here, we describe the isolation and characterization of cDNAs encoding NAP1-like proteins from the monocotyledon rice ( Oryza sativa L.) and the dicotyledon tobacco ( Nicotiana tabacum L.). Northern-blot analysis demonstrated that the two rice NAP1-like genes are predominantly expressed in stem tissues such as root and shoot apical meristems as well as in young flowers. During the cell cycle, all four tobacco NAP1-like genes are highly expressed, with one of them showing a slightly increased expression at the G1/S transition. These results are consistent with a role for plant NAP1-like proteins in cell division. In vitro binding assays revealed that different NAP1-like proteins bind, with distinct relative binding strengths, to different classes of histone. Intracellular localization analyses showed that some NAP1-like proteins could be targeted into the nucleus whereas others are exclusively cytoplasm-localized. It is thus likely that different plant NAP1-like proteins have distinct functions in vivo. Plant NAP1-like proteins were observed to concentrate around the metaphase plate and in the phragmoplast, suggesting a role in mitotic events and cytokinesis.

Amino Acid Sequence↗

PubMed2002

The subcellular localization of an unusual rice calmodulin isoform, OsCaM61, depends on its prenylation status.

Calmodulin (CaM) is a small Ca2+-binding protein highly conserved in eukaryotes. We have reported previously a novel rice CaM-like protein (OsCaM61) which contains an N-terminal CaM domain and a C-terminal extension with a potential prenylation site. Here we report in vitro activity assays confirm OsCaM61 as a functional CaM. Using the green fluorescent protein (GFP) as a visual marker, we further studied the subcellular localization of OsCaM61 in stably transformed tobacco cells. The GFP-OsCaM61 fusion protein was membrane-associated whereas OsCaM61-GFP was mainly detected in the nucleoplasm. GFP-OsCaM61 was transported into the nucleoplasm upon a block in isoprenoid biosynthesis by mevinolin treatment of cells. These results indicate that the prenylated OsCaM61 molecules are mainly membrane-associated whereas its unprenylated counterparts are transported into the nucleoplasm. Thus, OsCaM61 may play functions in co-ordinating Ca2+ signaling with isoprenoid metabolism.

Amino Acid Sequence↗

PubMed2002

The plant E2F-Rb pathway and epigenetic control.

Plants and animals use the E2F-Rb pathway as a major mechanism of control in the decision to continue or stop cell division. The E2F-Rb pathway controls the G1-to-S-phase transition by the timely activation of genes involved in DNA synthesis and cell-cycle control. Recent findings reveal that the E2F-Rb pathway communicates with chromatin-remodelling factors in the control of transcription and cell-cycle progression. This article highlights the fast-moving advances in the molecular and functional characterization of plant E2F proteins, and in our understanding of how the E2F-Rb pathway is activated and repressed.

Arabidopsis↗

PubMed2002

Null mutation of AtCUL1 causes arrest in early embryogenesis in Arabidopsis.

The SCF (for SKP1, Cullin/CDC53, F-box protein) ubiquitin ligase targets a number of cell cycle regulators, transcription factors, and other proteins for degradation in yeast and mammalian cells. Recent genetic studies demonstrate that plant F-box proteins are involved in auxin responses, jasmonate signaling, flower morphogenesis, photocontrol of circadian clocks, and leaf senescence, implying a large spectrum of functions for the SCF pathway in plant development. Here, we present a molecular and functional characterization of plant cullins. The Arabidopsis genome contains 11 cullin-related genes. Complementation assays revealed that AtCUL1 but not AtCUL4 can functionally complement the yeast cdc53 mutant. Arabidopsis mutants containing transfer DNA (T-DNA) insertions in the AtCUL1 gene were shown to display an arrest in early embryogenesis. Consistently, both the transcript and the protein of the AtCUL1 gene were found to accumulate in embryos. The AtCUL1 protein localized mainly in the nucleus but also weakly in the cytoplasm during interphase and colocalized with the mitotic spindle in metaphase. Our results demonstrate a critical role for the SCF ubiquitin ligase in Arabidopsis embryogenesis.

Amino Acid Sequence↗

PubMed2002

[Anti-tussive and expectorant effects of Liangyuan Pipagao,a Chinese medicine]

OBJECTIVE: To evaluate the pharmacological effects of Liangyuan Pipagao on cough reflex and ciliary action. Liangyuan Pipagao is a compound preparation of traditional Chinese medicine. METHODS: Cough was induced by aerosol citric acid in guinea pigs and aerosol capsacin in mice. Excretion function of the airway in mice was determined by phenol red method. Ciliary movement function of frog esophagus was examined by a migration method of charcoal granules. RESULTS: Liangyuan Pipagao inhibited both the citric acid-induced cough in guinea pigs and capsacin-induced cough in mice. ID(50)value 2.64 g/kg (95%Cl1.12 approximately 6.19) and 11.40 g/kg (95%Cl5.76 approximately 22.58) respectively. Further, Liangyuan Pipagao increased phenol red excretion in mice airways and stimulated ciliary action of frog esophagusin a dose-dependent fashion. ED(50) value 7.70 g/kg (95%Cl 4.62 approximately 12.83) and EC(25) value 1.07 X 10(-4) (95% Cl 0.394 approximately 2.92x10(-4)) respectively. CONCLUSION: Liangyuan Pipagao a traditional Chinese medicine may have anti-tussive as well as expectorant actions.

Journal Article↗

PubMed2002

Effects of cyclosporin A by aerosol on airway hyperresponsiveness and inflammation in guinea pigs.

AIM: To study cyclosporin A (CsA) by aerosol for anti-asthmatic effects in guinea pigs. METHODS: PC200 changes of lung resistance (RL) in the antigen-challenged sensitized guinea pig induced by acetylcholine (ACh) or histamine, and eosinophils changes in bronchoalveolar lavage fluid (BALF) and pulmonary histologic section induced by antigen in vivo in sensitized guinea pigs were investigated. RESULTS: Pretreatment with CsA 10 g/L and 20 g/L by aerosol but not with CsA 5 g/L, dexamethasone (DXM) 0.5 mg/kg by ip increased PC200 value and prevented ACh or histamine-induced airway hyperresponsiveness. However, CsA 5 g/L also prevented histamine-induced airway hyperresponsiveness. CsA 10 g/L, 20 g/L and DXM 0.5 mg/kg reduced markedly eosinophil accumulation in BALF. The lymphocyte accumulation induced by antigen was not changed significantly by CsA and DXM tested. DXM 0.5 mg/kg increased number of neutrophil in the BALF. There was a statistical significance comparison with CsA groups. In the pulmonary histological studies, CsA 20 g/L and DXM 0.5 mg/kg also inhibited eosinophil infiltration in the epithelium and subepithelial connective tissue of bronchi and bronchioles. CONCLUSION: Anti-inflammation and anti-hyperresponsiveness of CsA by aerosol in animal model offered an experimental evidence for airway inhalation of CsA in the treatment of asthma.

Acetylcholine↗

PubMed2002

Correlative changes of interferon-gamma and interleukin-4 between cortical layer and pulmonary airway of sensitized rats.

AIM: To explore correlation of T helper 1 (Th1) and Th2 cytokine between the cortical layer and pulmonary airway in ovalbumin-induced rat asthma model. METHODS: Aerosol antigen-induced changes of inflammation in bronchoalveolar lavage fluids (BALF) and pulmonary histologic section in sensitized rats were investigated. Changes of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) in BALF and cortical layer homogenates were determined by ELISA. RESULTS: The number of inflammatory cells in BALF in antigen challenged group was significantly higher than control group (P <0.05). Dexamethasone (DXM, 0.5 mg/kg, ip) markedly reduce total leukocyte numbers in BALF, and almost completely inhibited eosinophil, lymphocyte accumulation. The score of histological examination (eosinophil infiltration, mucous edema and epithelial lesion) in antigen challenged group was significantly higher than control group (P <0.05). DXM (0.5 mg/kg, ip) reduced the numbers of eosinophils and improved mucous edema and epithelial lesion of bronchi and bronchioles. In addition, our results demonstrated decreased IFN-gamma level accompanied by increased IL-4 level that resulted in a decreased IFN-gamma/IL-4 ratio in the BALF after the sensitized rats were challenged with aerosol antigen. Meanwhile, there was a similar change of IFN-gamma and IL-4 in cortical layer homogenates. DXM (0.5 mg/kg, ip) could reverse IFN-gamma/IL-4 ratio in the BALF and cortical layer homogenates in the model. CONCLUSION: The results showed a significant interplay changes of Th1 and Th2 cytokine between central nervous system and pulmonary airway in the asthmatic inflammatory model.

Animals↗