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Ji Sun

Publications and source records attributed to Ji Sun.

16 recordsLinked to original sources
PubMed2026

Genome-Wide Analysis of the PYL Gene Family and Its Expression Dynamics in Response to Abscisic Acid in Tomato.

The plant hormone abscisic acid (ABA) plays a crucial role throughout the plant life cycle and in adaptive responses to environmental stresses. The pyrabactin resistance 1-like (PYR/PYL/RCAR) proteins act as key regulators in the ABA signal transduction pathway by functioning as direct receptors for ABA. Although PYL genes have been identified in a variety of plant species, their evolutionary and structural characteristics in tomatoes (Solanum lycopersicum) remain elusive. To address this gap, we identified nine SlPYL genes, which were classified into three subfamilies: I (two genes), II (three genes), and III (four genes), and their encoded proteins were predicted to be primarily localized in the cytosol and chloroplast. Structural analysis revealed diverse exon-intron organizations along with five conserved motifs. All identified SlPYLs contained the START domain (PF10604), validating their identity as actual PYL proteins. Prediction of cis-acting regulatory elements in SlPYL's promoter regions was found to be associated with light responsiveness, hormone signaling, stress responses, and plant growth and development. Prediction of post-translational modification sites indicated that SlPYLs are predominantly phosphorylated and acetylated at serine and lysine residues, respectively. Tertiary structure modeling demonstrated conserved three-dimensional architectures among SlPYL proteins, supporting their functional conservation. Expression profiling revealed that specific SlPYL genes exhibit distinct expression patterns across different tissues (root, leaf, and bud) following ABA treatment, indicating functional diversification. Considering the well-established negative correlation between ABA accumulation and bud outgrowth, the ABA-induced differential expression (3~5-fold) of some SlPYL genes (SlPYL3, SlPYL4, SlPYL7, and SlPYL8), particularly in bud tissues after 24 hpt, suggests a potential role in ABA-mediated suppression of bud outgrowth. However, these functional inferences are primarily based on genome-wide computational analyses and expression profiling and therefore require further experimental validation.

Solanum lycopersicum↗
PubMed2007

Structural insight into the ESCRT-I/-II link and its role in MVB trafficking.

ESCRT (endosomal sorting complex required for transport) complexes orchestrate efficient sorting of ubiquitinated transmembrane receptors to lysosomes via multivesicular bodies (MVBs). Yeast ESCRT-I and ESCRT-II interact directly in vitro; however, this association is not detected in yeast cytosol. To gain understanding of the molecular mechanisms of this link, we have characterised the ESCRT-I/-II supercomplex and determined the crystal structure of its interface. The link is formed by the vacuolar protein sorting (Vps)28 C-terminus (ESCRT-I) binding with nanomolar affinity to the Vps36-NZF-N zinc-finger domain (ESCRT-II). A hydrophobic patch on the Vps28-CT four-helix bundle contacts the hydrophobic knuckles of Vps36-NZF-N. Mutation of the ESCRT-I/-II link results in a cargo-sorting defect in yeast. Interestingly, the two Vps36 NZF domains, NZF-N and NZF-C, despite having the same core fold, use distinct surfaces to bind ESCRT-I or ubiquitinated cargo. We also show that a new component of ESCRT-I, Mvb12 (YGR206W), engages ESCRT-I directly with nanomolar affinity to form a 1:1:1:1 heterotetramer. Mvb12 does not affect the affinity of ESCRT-I for ESCRT-II in vitro. Our data suggest a complex regulatory mechanism for the ESCRT-I/-II link in yeast.

Amino Acid Sequence↗
PubMed2007

Structural studies of phosphoinositide 3-kinase-dependent traffic to multivesicular bodies.

Three large protein complexes known as ESCRT I, ESCRT II and ESCRT III drive the progression of ubiquitinated membrane cargo from early endosomes to lysosomes. Several steps in this process critically depend on PtdIns3P, the product of the class III phosphoinositide 3-kinase. Our work has provided insights into the architecture, membrane recruitment and functional interactions of the ESCRT machinery. The fan-shaped ESCRT I core and the trilobal ESCRT II core are essential to forming stable, rigid scaffolds that support additional, flexibly-linked domains, which serve as gripping tools for recognizing elements of the MVB (multivesicular body) pathway: cargo protein, membranes and other MVB proteins. With these additional (non-core) domains, ESCRT I grasps monoubiquitinated membrane proteins and the Vps36 subunit of the downstream ESCRT II complex. The GLUE (GRAM-like, ubiquitin-binding on Eap45) domain extending beyond the core of the ESCRT II complex recognizes PtdIns3P-containing membranes, monoubiquitinated cargo and ESCRT I. The structure of this GLUE domain demonstrates that it has a split PH (pleckstrin homology) domain fold, with a non-typical phosphoinositide-binding pocket. Mutations in the lipid-binding pocket of the ESCRT II GLUE domain cause a strong defect in vacuolar protein sorting in yeast.

Amino Acid Motifs↗
PubMed2006

New component of ESCRT-I regulates endosomal sorting complex assembly.

The endosomal sorting complex required for transport (ESCRT) complexes play a critical role in receptor down-regulation and retroviral budding. Although the crystal structures of two ESCRT complexes have been determined, the molecular mechanisms underlying the assembly and regulation of the ESCRT machinery are still poorly understood. We identify a new component of the ESCRT-I complex, multivesicular body sorting factor of 12 kD (Mvb12), and demonstrate that Mvb12 binds to the coiled-coil domain of the ESCRT-I subunit vacuolar protein sorting 23 (Vps23). We show that ESCRT-I adopts an oligomeric state in the cytosol, the formation of which requires the coiled-coil domain of Vps23, as well as Mvb12. Loss of Mvb12 results in the disassembly of the ESCRT-I oligomer and the formation of a stable complex of ESCRT-I and -II in the cytosol. We propose that Mvb12 stabilizes ESCRT-I in an oligomeric, inactive state in the cytosol to ensure that the ordered recruitment and assembly of ESCRT-I and -II is spatially and temporally restricted to the surface of the endosome after activation of the MVB sorting reaction.

Cell Compartmentation↗
PubMed2006

Quantitative analysis of lovastatin in capsule of Chinese medicine monascus by capillary zone electrophoresis with UV-vis detector.

A capillary zone electrophoresis (CZE) method was developed for the quantitative analysis of lovastatin (Lvt) in capsule of monascus-Chinese medicine. Lvt in the capsule was separated using an electrolyte system consisting of 16% ethanol (v/v) in 60 mM Gly-sodium hydroxide buffer, pH 10.5, 16 kV applied voltage, 238 nm detection wavelength with a capillary of 51 cm x 75 microm i.d (43 cm to detector). Under the optimized conditions, the linear response of Lvt concentration ranges from 4.0 to 240 microg/mL with high correlation coefficient (r=0.9998, n=9), the limits of detection (LOD) and quantification (LOQ) for Lvt are 0.73 and 2.42 microg/mL, the precision values (expressed as R.S.D.) of intra-day and inter-day are 1.40-2.12% and 1.47-3.88%, respectively. The recoveries of the analyte at three concentration levels are 90.28-100.71%. The developed method can be well used for the quantification of Lvt in the drug in commercial formulations.

Buffers↗
PubMed2006

ESCRT-I core and ESCRT-II GLUE domain structures reveal role for GLUE in linking to ESCRT-I and membranes.

ESCRT complexes form the main machinery driving protein sorting from endosomes to lysosomes. Currently, the picture regarding assembly of ESCRTs on endosomes is incomplete. The structure of the conserved heterotrimeric ESCRT-I core presented here shows a fan-like arrangement of three helical hairpins, each corresponding to a different subunit. Vps23/Tsg101 is the central hairpin sandwiched between the other subunits, explaining the critical role of its "steadiness box" in the stability of ESCRT-I. We show that yeast ESCRT-I links directly to ESCRT-II, through a tight interaction of Vps28 (ESCRT-I) with the yeast-specific zinc-finger insertion within the GLUE domain of Vps36 (ESCRT-II). The crystal structure of the GLUE domain missing this insertion reveals it is a split PH domain, with a noncanonical lipid binding pocket that binds PtdIns3P. The simultaneous and reinforcing interactions of ESCRT-II GLUE domain with membranes, ESCRT-I, and ubiquitin are critical for ubiquitinated cargo progression from early to late endosomes.

Amino Acid Sequence↗
PubMed2006

Structural and functional organization of the ESCRT-I trafficking complex.

The endosomal sorting complex required for transport (ESCRT) complexes are central to receptor downregulation, lysosome biogenesis, and budding of HIV. The yeast ESCRT-I complex contains the Vps23, Vps28, and Vps37 proteins, and its assembly is directed by the C-terminal steadiness box of Vps23, the N-terminal half of Vps28, and the C-terminal half of Vps37. The crystal structures of a Vps23:Vps28 core subcomplex and the Vps23:Vps28:Vps37 core were solved at 2.1 and 2.8 A resolution. Each subunit contains a structurally similar pair of helices that form the core. The N-terminal domain of Vps28 has a hydrophobic binding site on its surface that is conformationally dynamic. The C-terminal domain of Vps28 binds the ESCRT-II complex. The structure shows how ESCRT-I is assembled by a compact core from which the Vps23 UEV domain, the Vps28 C domain, and other domains project to bind their partners.

Amino Acid Motifs↗
PubMed2005

[An observation on long-term results of subtotal laryngectomy with preservation of an arytenoid cartilage].

OBJECTIVE: To discuss the long-term results of the subtotal laryngectomy with preservation of an arytenoids cartilage. METHODS: The long-term results of the subtotal laryngectomy with preservation of an arytenoids cartilage were analysed in 82 patients with squamous cell carcinoma of larynx (stage III 73 cases, IV 9 cases; supraglottic type 71 cases, glottic 6, transglottic 5). RESULTS: The functions of speech and deglutition were recovered in 82 patients, and the respirations were normal in 69 of 82 cases (84.2%). Pharyngeal fistula appeared in 2 cases, and the infection of incision wound in 6, but all of them were cured by conservative treatment. All of 82 cases were followed-up for more than 5 years, 5 cases were lost follow-up, so the follow-up rate was 93.3%. 26 patients died of various causes during 5 years after operation. 5 of 26 cases died of local recurrence of laryngeal carcinoma, neck metastasis in 4, others in 4 (cardiac insufficiency, myocardiac infarction, lungs metastasis, rectal carcinoma 1 case, respectively) unknown in 4, lost follow-up in 5.68 patients were followed-up for more than 10 years, 30 cases were dead (26 cases who died of various causes included during 5 years after operation; died of local recurrence in larynx was 1 case, unknown 2, lost follow-up 1, during 5 approximately 10 years after surgery). 5, 10 years survival rates were 68.3% (56/82) and 55.9% (38/68), respectively. CONCLUSIONS: Subtotal laryngectomy with preservation of an arytenoids cartilage is recommended for T3 and some elective T4 laryngeal carcinoma.

Adult↗
PubMed2005

[Pathological feature and management of occult lymphatic metastasis in supraglottic carcinoma].

OBJECTIVE: To study the pathologic feature and management methods of occult lymphatic metastasis in patients with supraglottic carcinoma. METHODS: The following are criteria of patients selection: (1) Supraglottic squamous cell carcinoma; (2) Clinical N0M0; (3) no preoperative radiotherapy and (or) chemotherapy. Thirty patients were recruited, male 19 cases, female 11; age: 40 - 72yr, average 54.8yr; T2 8 cases, T3 18, T4 4 (by UICC 1997). Ipsilateral supraomohyoid neck dissections were performed in all cases. Lymph nodes were studied histologically according to the levels of dissection. RESULTS: Six of 30 cases were positive nodes histologically in first operation, 3 were occurrence neck metastasis in opposite side during follow ups. Occult metastasis rate was 20% (6/30) ipsilaterdly and 10% contralaterally. 527 lymph nodes were collected in all of 30 patients, average 17.6 nodes in every side neck. Ten positive lymph nodes histologically were harvested. The distribution of metastatic lymph nodes was 9 in level II, 1 in level III, no in level I. N0 recurrence in larynx and (or) at the neck after dissection. Two years survival rates was 86.7% (26/30) without tumor. CONCLUSION: Occult metastasis rate of supraglottic carcinoma is as high as 30%. The selective lateral neck dissection of level II, III and occasionally, level IV was recommended.

Adult↗
PubMed2004

Structure of the ESCRT-II endosomal trafficking complex.

The multivesicular-body (MVB) pathway delivers transmembrane proteins and lipids to the lumen of the endosome. The multivesicular-body sorting pathway has crucial roles in growth-factor-receptor downregulation, developmental signalling, regulation of the immune response and the budding of certain enveloped viruses such as human immunodeficiency virus. Ubiquitination is a signal for sorting into the MVB pathway, which also requires the functions of three protein complexes, termed ESCRT-I, -II and -III (endosomal sorting complex required for transport). Here we report the crystal structure of the core of the yeast ESCRT-II complex, which contains one molecule of the Vps protein Vps22, the carboxy-terminal domain of Vps36 and two molecules of Vps25, and has the shape of a capital letter 'Y'. The amino-terminal coiled coil of Vps22 and the flexible linker leading to the ubiquitin-binding NZF domain of Vps36 both protrude from the tip of one branch of the 'Y'. Vps22 and Vps36 form nearly equivalent interactions with the two Vps25 molecules at the centre of the 'Y'. The structure suggests how ubiquitinated cargo could be passed between ESCRT components of the MVB pathway through the sequential transfer of ubiquitinated cargo from one complex to the next.

Binding Sites↗
PubMed2004

Myelin-associated glycoprotein (Siglec-4) expression is progressively and selectively decreased in the brains of mice lacking complex gangliosides.

Myelin-associated glycoprotein (MAG, Siglec-4) is a quantitatively minor membrane component expressed preferentially on the innermost myelin wrap, adjacent to the axon. It stabilizes myelin-axon interactions by binding to complementary ligands on the axolemma. MAG, a member of the Siglec family of sialic acid-binding lectins, binds specifically to gangliosides GD1a and GT1b, which are the major sialoglycoconjugates on mammalian axons. Mice with a disrupted Galgt1 gene lack UDP-GalNAc:GM3/GD3 N-acetylgalactosaminyltransferase (GM2/GD2 synthase) and fail to express complex brain gangliosides, including GD1a and GT1b, instead expressing a comparable amount of the simpler gangliosides GM3, GD3, and O-acetyl-GD3. Galgt1-null mice produce similar amounts of total myelin compared to wild-type mice, but as the mice age, they exhibit axon degeneration and dysmyelination with accompanying motor behavioral deficits. Here we report that Galgt1-null mice display progressive and selective loss of MAG from the brain. At 1.5 months of age, MAG expression was similar in Galgt1-null and wild-type mice. However, by 6 months of age MAG was decreased approximately 60% and at 12 months of age approximately 70% in Galgt1-null mice compared to wild-type littermates. Expression of the major myelin proteins (myelin basic protein and proteolipid protein) was not reduced in Galgt1-null mice compared to wild type. MAG mRNA expression was the same in 12-month-old Galgt1-null compared to wild-type mice, an age at which MAG protein expression was markedly reduced. We conclude that the maintenance of MAG protein levels depends on the presence of complex gangliosides, perhaps due to enhanced stability when MAG on myelin binds to its complementary ligands, GD1a and GT1b, on the apposing axon surface.

Animals↗
PubMed2004

Ubiquitin interactions of NZF zinc fingers.

Ubiquitin (Ub) functions in many different biological pathways, where it typically interacts with proteins that contain modular Ub recognition domains. One such recognition domain is the Npl4 zinc finger (NZF), a compact zinc-binding module found in many proteins that function in Ub-dependent processes. We now report the solution structure of the NZF domain from Npl4 in complex with Ub. The structure reveals that three key NZF residues (13TF14/M25) surrounding the zinc coordination site bind the hydrophobic 'Ile44' surface of Ub. Mutations in the 13TF14/M25 motif inhibit Ub binding, and naturally occurring NZF domains that lack the motif do not bind Ub. However, substitution of the 13TF14/M25 motif into the nonbinding NZF domain from RanBP2 creates Ub-binding activity, demonstrating the versatility of the NZF scaffold. Finally, NZF mutations that inhibit Ub binding by the NZF domain of Vps36/ESCRT-II also inhibit sorting of ubiquitylated proteins into the yeast vacuole. Thus, the NZF is a versatile protein recognition domain that is used to bind ubiquitylated proteins during vacuolar protein sorting, and probably many other biological processes.

Amino Acid Sequence↗
PubMed2002

The effect of selective inhibition of cyclooxygenase (COX)-2 on acute cardiac allograft rejection.

BACKGROUND: Using a rat (Lewis-Wistar Furth) abdominal heterotopic transplantation model, we reported previously that the expression of cyclooxygenase (COX)-2 is increased in parallel with that of nitric oxide synthase (NOS)-2 during cardiac allograft rejection. METHODS: To investigate effects of COX-2 inhibition in this model, allograft recipients were treated orally (PO) with 5 mg/kg per day of the tetra substituted furanone selective COX-2 inhibitor 5,5-dimethyl-3-(3 fluorophenyl)-4-(4 methylsulfonal) phenyl-2 (5H)-furanone (DFU) in 1% methyl cellulose solution. RESULTS: In the treated animals, allograft survival was increased from 6.3+/-0.5 to 12.6+/-2.6 days (P = .001). At days 3 and 5 posttransplantation, there were reductions in the extent of the inflammatory infiltrate, endovasculitis, myocardial edema, and cardiomyocyte damage in rejecting allografts. The mean numbers of apoptotic cardiomyocytes determined with the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) technique were significantly reduced in DFU-treated grafts compared with untreated controls (P < 0.05). At day 3 posttransplantation, prostaglandin E2 synthesis by myocardial slices incubated with 100 microM bradykinin was reduced from 1,097+/-156 to 153+/-63 pg/mg of protein in the treated allografts (P < .005). At day 5, COX-2 protein and mRNA together with COX-2, NOS-2, and nitrotyrosine immunostaining in damaged cardiomyocytes were diminished in treated versus control grafts. CONCLUSION: The data indicate that the inhibition of COX-2 prolongs allograft survival and reduces myocardial damage and inflammation during acute cardiac allograft rejection.

Acute Disease↗
PubMed2002

Effects of selective inhibitors of nitric oxide synthase-2 dimerization on acute cardiac allograft rejection.

BACKGROUND: Nitric oxide synthase-2 (NOS2) is expressed during acute cardiac allograft rejection in association with myocardial inflammation, contractile dysfunction, and death of cardiomyocytes by necrosis and apoptosis. Recently, allosteric inhibitors of NOS2 monomer dimerization that block NOS2 activity have been developed. METHODS AND RESULTS: To investigate effects of selective NOS2 blockade, 15 mg/kg of BBS-1 or BBS-2 was administered twice daily subcutaneously to rats starting the day of heterotopic heart transplantation. Cardiac allograft survival was increased significantly, from 6.8 days in controls to 13.3 and to 14.2 days in NOS2-inhibited allografts. At day 5 after heart transplantation, synthesis of NOx was reduced by 53%. There were significantly fewer T lymphocytes and macrophages in the inflammatory infiltrate, as well as less edema and cardiomyocyte damage, and the International Society of Heart and Lung Transplantation score fell from 5 to 4 and 3.5. NOS2 and nitrotyrosine immunostaining and the mean numbers of apoptotic cells and of apoptotic cardiomyocytes were significantly diminished in the treated allografts. CONCLUSIONS: The data indicate that selective inhibition of NOS2 dimerization prolongs survival and reduces myocardial inflammation and cardiomyocyte damage in acute cardiac allograft rejection.

Acute Disease↗
PubMed1996

Comparative Kinetic Analysis of Reversible Intermolecular Electron-Transfer Reactions between a Series of Pentaammineruthenium Complexes and Cytochrome c.

In this kinetic and thermodynamic study, the reversible outer-sphere electron-transfer reactions between a series of Ru(NH(3))(5)L(3+/2+) complexes (L = etpy, py, lut) (etpy = 4-ethylpyridine; py = pyridine; lut = 3,5-lutidine) and cytochrome c were investigated as a function of ionic strength, buffer, pH, temperature, and pressure. Due to the low driving forces of these systems, it was possible to study all the reactions in both redox directions. The observed rate constants for various L are correlated on the basis of the ability of ligands on the ruthenium complex to penetrate the heme groove on cytochrome c. The measurements as a function of pressure enabled the construction of volume profiles for all investigated systems. The activation volumes for all of these processes are very similar: between -14.9 and -17.8 cm(3) mol(-)(1) for the reduction and between +14.7 and +17.8 cm(3) mol(-)(1) for the oxidation of the protein by Ru(NH(3))(5)L(2+/)(3+), respectively. The overall reaction volume varies between 27 and 35 cm(3) mol(-)(1), from which it follows that the transition state lies exactly halfway between reactant and product states on a volume basis in all cases. There is good agreement throughout between kinetic and thermodynamic data.

Journal Article↗