Biomedical subjects

Liping Ren

Publications and source records attributed to Liping Ren.

13 recordsLinked to original sources

PubMed2005

Cell wall remodeling at the fission yeast cell division site requires the Rho-GEF Rgf3p.

Cytokinesis in Schizosaccharomyces pombe is accompanied by several stages of cell wall remodeling at the division site. Coincident with actomyosin ring constriction, primary and secondary septa are deposited and then the primary septum is degraded to release daughter cells from one another. These steps require the activities of glucan synthases and glucanases, respectively, which must be coordinated with one another to prevent cell lysis. The lad1-1 mutation undergoes cell lysis specifically at cell division owing to the absence of the Rgf3p Rho1-guanine nucleotide exchange factor (GEF) at the division site. Electron microscopic analysis indicates that lysis occurs only as the primary septum begins to be degraded. Overproduction of either Rho1p or the previously uncharacterized Rab-GTPase-activating protein (GAP) involved in secretion, Gyp10p, suppresses lad1-1 lethality. Rgf3p is periodically produced in an Ace2p-dependent manner and localizes to the medial region of the cell early in mitosis, a pattern of expression distinct from the highly related Rho-GEF, Rgf1p. Although rgf1+ is not an essential gene, it is synthetically lethal with rgf2-deleted cells whereas no negative genetic interactions were detected between rgf2-deleted cells and lad1-1. Our data suggest that the three closely related fission yeast Rho-GEF molecules perform two distinct essential functions. Rgf3p appears necessary to stimulate Rho1p-mediated activation of a glucan synthase crucial after septation for proper new cell-end formation.

Cell Division↗

PubMed2005

Analysis of the role of phosphorylation in fission yeast Cdc13p/cyclinB function.

The Cdk1p-cyclin B complex drives entry into mitosis in all eukaryotes. Cdc13p is the single essential cyclin in Schizosaccharomyces pombe and a member of the cyclin B family. Cdc13p abundance rises during G(2)-phase and falls as cells progress through mitosis and G(1). Cdc13p degradation, mediated by the anaphase-promoting complex, is an important mechanism of Cdk1p inhibition and mitotic exit. Cdk1p-cyclin B1 complexes shuttle between the nucleus and cytoplasm, and preventing nuclear accumulation of Cdk1p-cyclin B1 in mammalian cells appears to be one mechanism of preventing entry into mitosis during a DNA damage-induced checkpoint delay. In vertebrates, phosphorylation plays a key role in regulating the intracellular distribution of cyclins. Previous mass spectrometric analysis identified sites of Cdc13p phosphorylation. Here, we have confirmed that these sites are the sole in vivo Cdc13p phosphorylation sites and have studied the role that phosphorylation plays in Cdc13p localization and function. Our data indicate that Cdc13p accumulates in the nucleolus in response to G(2) checkpoint delays, rather than in the cytoplasm, and that phosphorylation plays no role in Cdc13p localization or function.

Alleles↗

PubMed2005

Dim1p is required for efficient splicing and export of mRNA encoding lid1p, a component of the fission yeast anaphase-promoting complex.

Schizosaccharomyces pombe Dim1p is required for maintaining the steady-state level of the anaphase-promoting complex or cyclosome (APC/C) component Lid1p and thus for maintaining the steady-state level and activity of the APC/C. To gain further insight into Dim1p function, we have investigated the mechanism whereby Dim1p influences Lid1p levels. We show that S. pombe cells lacking Dim1p or Saccharomyces cerevisiae cells lacking its ortholog, Dib1p, are defective in generalized pre-mRNA splicing in vivo, a result consistent with the identification of Dim1p as a component of the purified yeast U4/U6.U5 tri-snRNP complex. Moreover, we find that Dim1p is part of a complex with the splicing factor Prp1p. However, although Dim1p is required for efficient splicing of lid1(+) pre-mRNA, circumventing the necessity for this particular function of Dim1p is insufficient for restoring normal Lid1p levels. Finally, we provide evidence that Dim1p also participates in the nuclear export of lid1(+) mRNA and that it is likely the combined loss of both of these two Dim1p functions which compromises Lid1p levels in the absence of proper Dim1p function. These data indicate that a mechanism acting at the level of mRNA impacts the functioning of the APC/C, a critical complex in controlling mitotic progression.

Anaphase-Promoting Complex-Cyclosome↗

PubMed2005

Structural and functional analysis of essential pre-mRNA splicing factor Prp19p.

U-box-containing Prp19p is an integral component of the Prp19p-associated complex (the nineteen complex, or NTC) that is essential for activation of the spliceosome. Prp19p makes numerous protein-protein contacts with other NTC components and is required for NTC stability. Here we show that Prp19p forms a tetramer in vitro and in vivo and we map the domain required for its oligomerization to a central tetrameric coiled-coil. Biochemical and in vivo analyses are consistent with Prp19p tetramerization providing an interaction surface for a single copy of its binding partner, Cef1p. Electron microscopy showed that the isolated Prp19p tetramer is an elongated particle consisting of four globular WD40 domains held together by a central stalk consisting of four N-terminal U-boxes and four coiled-coils. These structural and functional data provide a basis for understanding the role of Prp19p as a key architectural component of the NTC.

Cell Cycle Proteins↗

PubMed2005

[Research advances on eco-chemical behaviors and toxicological effects of cadmium in root-soil interface].

Many active substances such as organic acids and enzymes excreted by living plant roots could induce a great difference of Eh and pH values between root-soil interface and non-rhizosphere soil, forming a special root-soil interface miniature environment. As a mini-type ecological area with most frequent exchanges of substances, root-soil interface plays a crucial role in their absorption, transformation, migration and eco-toxicological effects. In this paper, the eco-chemical behaviors of Cd in root-soil interface affected by the change of pH, Eh and root secretion, and its eco-toxicological effects on microorganisms and enzymes in root-soil interface were reviewed, based on the related research advances in recent decade. The shortages in relevant fields were pointed out, and the scientific problems to be researched in the future were suggested.

Cadmium↗

PubMed2004

Tandem affinity purification and identification of protein complex components.

As with the budding yeast Saccharomyces cerevisiae, the completion of the Schizosaccharomyces pombe genome sequence has opened new opportunities to investigate the functional organization of a eukaryotic cell. These include analysis of gene expression patterns, comprehensive gene knockout and synthetic lethal screens, global protein localization analysis, and direct protein interaction mapping. We describe here the tandem affinity purification or TAP approach combined with DALPC mass spectrometry to identify components of protein complexes as we have applied it to S. pombe. This approach can theoretically be applied to the entire proteome as has been done in S. cerevisiae to gain insight into functional protein assemblies and to elucidate functions of uncharacterized proteins.

Multiprotein Complexes↗

PubMed2003

[Cu adsorption by phaeozem and burazem].

Studies on the thermodynamics and kinetics of copper (Cu2+) adsorption by phaeozem and burozem showed that that the adsorption of Cu2+ by these two soils was increased with the increasing concentration of Cu2+ within the range of Cu2+ concentrations used in the experiment, but the amount of Cu2+ adsorbed and fixed on phaeozem was much higher than that on burozem. When the test Cu2+ concentration in adsorption equilibrium was 95 mg.kg-1, its adsorption by burozem was nearly 3720 mg.kg-1, whereas by phaeozem was as high as 6076 mg.kg-1. Under the highest CuCl2 treatment of 400 mg.kg-1, Cu2+ adsorbed by phaeozem and burozem was 6159.0 mg.kg-1 and 4736.6 mg.kg-1, respectively. The adsorption of Cu2+ by the test soils could significantly conform to the Freundlich and Temkin equation, while Langmuir equation was not applicable to describe the isothermal adsorption processes of Cu2+ by the two soils. The adsorption of Cu2+ by the test soils was very rapid, which could reach its balance after 15-20 min. The adsorption within the first 2 min at its beginning stage accounted for 90% of the Cu equilibrium adsorption. The adsorptive rate of Cu2+ by phaeozem was decreased more quickly than that by burozem with the time. The two-constant equation was the optimal model to describe the adsorption of Cu2+. The other models in point were first-order dynamic equations and Elovich equations, whereas parabolic diffusion equations were not suitable ones.

Adsorption↗

PubMed2003

[Performance of a novel combined flocculant HECES].

Combined flocculants with higher environmental safety and lower ecological risk are urgently required in the process of water and wastewater treatment. HECES, a kind of flocculants with high effect and high ecological safety was synthesized by natural and biodegradable polysaccharide starch of corn and inorganic aluminium salt. Flocculent performance includes sediment character and turbidity removal rate. The jar test results showed that the flocculent performance of HECES with the dose of 3.0 mg.L-1 was prior to the combined adding 4.5 mg.L-1 PAC and 1.0 mg.L-1 PAM in treating kaolin suspensions. The optimal concentration of HECES was 8.0 mg.L-1 and 4.0 mg.L-1 in treating domestic wastewater and municipal effluent respectively, with the comparison to 50% an 40% of PAC, the removal rate of turbidity reached 95% and 99%, respectively. It was also identified that the optimal concentration required to effect flocculation depended on kaolin concentration, and on the character of the wastewater within the range examined. It could be more effective to treat wastewater with higher concentration of HECES. The flocculating performance would be better at pH 4.0-9.5. The superior ecological safety of HECES was due to its lower dosage and its lower concentration of residual activated aluminium.

Flocculation↗

PubMed2002

[Eco-toxicological effects of heavy metals on the inhibition of seed germination and root elongation of Chinese cabbages in soils].

The Eco-toxicity effects of individual Cu, Zn, Pb and Cd on the inhibition of seed germination and root elongation of Chinese cabbages (Brassica pekimensis) were tested in four types of soils (red loam soils, meadow brown soils, chestnut soils and dark brown soils) and water solution. The combined effects of heavy metals pollution were determined with meadow brown soils. Results indicated that with same concentration, the inhibition rates of heavy metals on root elongation of Chinese cabbages are stronger than that on the seed germination. The inhibition effects of heavy metals on the root elongation of Chinese cabbages in soils are much lower than that in water, indicating that soils play an important role of buffering on heavy metals pollution. Inhibition rates of heavy metals on the root elongation (IRHMRE) of Chinese cabbages are significantly negative related with the contents of organic matter (OR) and Kjedahl-nitrogen (K-N) in soils, however, there is no significant related between IRHMRE and soil pH, so does the content of T-K. In the concentrations that result in the irritated effect in the single form of Cu, Zn, Pb and Cd pollution, synergic effects are produced significantly when four heavy metals are combined. As the results, the threshold values that result in the inhibition effects on root elongation in Chinese cabbages decrease markedly.

Brassica↗

PubMed2002

Proteomics analysis reveals stable multiprotein complexes in both fission and budding yeasts containing Myb-related Cdc5p/Cef1p, novel pre-mRNA splicing factors, and snRNAs.

Schizosaccharomyces pombe Cdc5p and its Saccharomyces cerevisiae ortholog, Cef1p, are essential Myb-related proteins implicated in pre-mRNA splicing and contained within large multiprotein complexes. Here we describe the tandem affinity purification (TAP) of Cdc5p- and Cef1p-associated complexes. Using transmission electron microscopy, we show that the purified Cdc5p complex is a discrete structure. The components of the S. pombe Cdc5p/S. cerevisiae Cef1p complexes (termed Cwfs or Cwcs, respectively) were identified using direct analysis of large protein complex (DALPC) mass spectrometry (A. J. Link et al., Nat. Biotechnol. 17:676-682, 1999). At least 26 proteins were detected in the Cdc5p/Cef1p complexes. Comparison of the polypeptides identified by S. pombe Cdc5p purification with those identified by S. cerevisiae Cef1p purification indicates that these two yeast complexes are nearly identical in composition. The majority of S. pombe Cwf proteins and S. cerevisiae Cwc proteins are known pre-mRNA splicing factors including core Sm and U2 and U5 snRNP components. In addition, the complex contains the U2, U5, and U6 snRNAs. Previously uncharacterized proteins were also identified, and we provide evidence that several of these novel factors are involved in pre-mRNA splicing. Our data represent the first comprehensive analysis of CDC5-associated proteins in yeasts, describe a discrete highly conserved complex containing novel pre-mRNA splicing factors, and demonstrate the power of DALPC for identification of components in multiprotein complexes.

Amino Acid Sequence↗

PubMed2002

[Comparative study on ecotoxicological indexes of crops exposure to reactive X-3B red dye].

Ecotoxicological indexes of wheat, Chinese cabbage and rice exposed to reactive X-3B red dye were studied using the experimental method of crop seed exposure. The results showed that reactions of the three crops to reactive X-3B red dye were different from each other. Based on the inhibition of seed gemination, the half effect concentration(IC50) of wheat, Chinese cabbage and rice was 8965, 7010 and 7514 mg.L-1. Based on the inhibition of root elongation, the IC50 of wheat, Chinese cabbage and rice was 6534, 5882 and 4570 mg.L-1. When seedlings were cultured for seven days after the gemination of seeds and the remaining seeds or husks were discarded, fresh and dry growing biomass of the three crops exposed to the dye was both decreased with the increasing the concentration of reactive X-3B red dye. However, the decrease rate of fresh biomass was higher than that of dry biomass. Biomass index of wheat was most sensitive to reactive X-3B red dye, followed by rice, and Chinese cabbage was most inertia when the crops were exposed to reactive X-3B red dye with the high concentration of 4500 and 5000 mg.L-1. As far as the tolerance of wheat, Chinese cabbage and rice to reactive X-3B red dye was concerned, wheat had the strongest tolerance, on the contrary rice had the wakestone.

Brassica↗

PubMed2002

[Acute toxicological effects of heavy metal pollution in soils on earthworms].

Acute and sub-acute lethal effects of single and combined Cu, Zn, Pb and Cd on earthworm was determined using meadow brown soil. Results indicated that the mortality of earthworm was significantly related with the concentrations of Cu and Zn in the soil (alpha = 0.05, RCu = 0.86, RPb = 0.87), and the inhibition rate of earthworm growth was significantly related with the concentration of Cu in the soil (alpha = 0.05, RCu = 0.84). There was no significant relation between the concentrations of other heavy metals tested and the death rate and the growth-inhibition rate. The degree of individual earthworm enduring the toxicity of heavy metals varied greatly. The threshold concentration of toxicity defined by statistical method, the level to conduce the death of individual earthworm was 300 mg.kg-1 for Cu, 1300 mg.kg-1 for Zn, 1700 mg.kg-1 for Pb, 300 mg.kg-1 for Cd. LC50 was 400-450 mg.kg-1 for Cu, 1500-1900 mg.kg-1 for Zn, 2350-2400 mg.kg-1 for Pb and 900 mg.kg-1 for Cd. Combined effects of single Cu, Zn, Pb and Cd to conduce more than 10% of the death rate of earthworm could result in 100% of the death rate of earthworm, thus showing the strong synergistic joint effect of the heavy metals.

Animals↗

PubMed2002

[Eco-toxicology of heavy metals on the inhibition of seed germination and root elongation of wheat in soils].

The eco-toxicity of Cu, Zn, Pb, and Cd in the single form was tested with four types of soils(red loam soils, meadow brown soils, chestnut soils, and dark brown soils) and their combined effect was determined with meadow brown soils. The results showed that with the same content of heavy metals, the root elongation was strongly inhabited than the seed germination, and it indicated that root was more sensitive to heavy metals pollution. The inhibition rate of heavy metals pollution on the root elongation (IRHMRE) of wheat was significantly related with the contents of organic matter (OR) and Kjedahl-nitrogen (K-N) in soils (R2OR = 0.91, R2K-N = 0.92). However, IRHMRE was not significantly related with soil pH as did with OR and K-N, so does the content of CEC (R2pH = 0.62, R2CEC = 0.60). Whether under the low concentration of Cu, Zn, Pb, and Cd resulted in an irritated effect in root elongation, or under high concentration resulted in an inhibition effect in the single form, an synergistic effect occurred in the combined form.

Cadmium↗