RNF4 is a poly-SUMO-specific E3 ubiquitin ligase required for arsenic-induced PML degradation

In acute promyelocytic leukaemia (APL), the promyelocytic leukaemia (PML) protein is fused to the retinoic acid receptor alpha (RAR). This disease can be treated effectively with arsenic, which induces PML modification by small ubiquitin-like modifiers (SUMO) and proteasomal degradation. Here we demonstrate that the RING-domain-containing ubiquitin E3 ligase, RNF4 (also known as SNURF), targets poly-SUMO-modified proteins for degradation mediated by ubiquitin. RNF4 depletion or proteasome inhibition led to accumulation of mixed, polyubiquitinated, poly-SUMO chains. PML protein accumulated in RNF4-depleted cells and was ubiquitinated by RNF4 in a SUMO-dependent fashion in vitro. In the absence of RNF4, arsenic failed to induce degradation of PML and SUMO-modified PML accumulated in the nucleus. These results demonstrate that poly-SUMO chains can act as discrete signals from mono-SUMOylation, in this case targeting a poly-SUMOylated substrate for ubiquitin-mediated proteolysis.     

Significant role for Fas in the pathogenesis of autoimmune diabetes

Programmed cell death represents an important pathogenic mechanism in various autoimmune diseases. Type I diabetes mellitus (IDDM) is a T cell-dependent autoimmune disease resulting in selective destruction of the beta cells of the islets of Langerhans. beta cell apoptosis has been associated with IDDM onset in both animal models and newly diagnosed diabetic patients. Several apoptotic pathways have been implicated in beta cell destruction, including Fas, perforin, and TNF-alpha. Evidence for Fas-mediated lysis of beta cells in the pathogenesis of IDDM in nonobese diabetic (NOD) mice includes: 1) Fas-deficient NOD mice bearing the lpr mutation (NOD-lpr/lpr) fail to develop IDDM; 2) transgenic expression of Fas ligand (FasL) on beta cells in NOD mice may result in accelerated IDDM; and 3) irradiated NOD-lpr/lpr mice are resistant to adoptive transfer of diabetes by cells from NOD mice. However, the interpretation of these results is complicated by the abnormal immune phenotype of NOD-lpr/lpr mice. Here we present novel evidence for the role of Fas/FasL interactions in the progression of NOD diabetes using two newly derived mouse strains. We show that NOD mice heterozygous for the FasL mutation gld, which have reduced functional FasL expression on T cells but no lymphadenopathy, fail to develop IDDM. Further, we show that NOD-lpr/lpr mice bearing the scid mutation (NOD-lpr/lpr-scid/scid), which eliminates the enhanced FasL-mediated lytic activity induced by Fas deficiency, still have delayed onset and reduced incidence of IDDM after adoptive transfer of diabetogenic NOD spleen cells. These results provide evidence that Fas/FasL-mediated programmed cell death plays a significant role in the pathogenesis of autoimmune diabetes.     

Recruitment of a foreign quinone into the A(1) site of photosystem I. II. Structural and functional characterization of phylloquinone biosynthetic pathway mutants by electron paramagnetic resonance and electron-nuclear double resonance spectroscopy

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance studies of the photosystem (PS) I quinone acceptor, A(1), in phylloquinone biosynthetic pathway mutants are described. Room temperature continuous wave EPR measurements at X-band of whole cells of menA and menB interruption mutants show a transient reduction and oxidation of an organic radical with a g-value and anisotropy characteristic of a quinone. In PS I complexes, the continuous wave EPR spectrum of the photoaccumulated Q(-) radical, measured at Q-band, and the electron spin-polarized transient EPR spectra of the radical pair P700(+) Q(-), measured at X-, Q-, and W-bands, show three prominent features: (i) Q(-) has a larger g-anisotropy than native phylloquinone, (ii) Q(-) does not display the prominent methyl hyperfine couplings attributed to the 2-methyl group of phylloquinone, and (iii) the orientation of Q(-) in the A(1) site as derived from the spin polarization is that of native phylloquinone in the wild type. Electron spin echo modulation experiments on P700(+) Q(-) show that the dipolar coupling in the radical pair is the same as in native PS I, i.e. the distance between P700(+) and Q(-) (25.3 +/- 0.3 A) is the same as between P700(+) and A(1)(-) in the wild type. Pulsed electron-nuclear double resonance studies show two sets of resolved spectral features with nearly axially symmetric hyperfine couplings. They are tentatively assigned to the two methyl groups of the recruited plastoquinone-9, and their difference indicates a strong inequivalence among the two groups when in the A(1) site. These results show that Q (i) functions in accepting an electron from A(0)(-) and in passing the electron forward to the iron-sulfur clusters, (ii) occupies the A(1) site with an orientation similar to that of phylloquinone in the wild type, and (iii) has spectroscopic properties consistent with its identity as plastoquinone-9.     

Using drift nets to capture early life stages and monitor spawning of the Yangtze River Chinese sturgeon (Acipenser sinensis)

A sampling system for capturing sturgeon eggs using a D-shaped bottom anchored drift net was used to capture early life stages (ELS) of Chinese sturgeon, Acipenser sinensis , and monitor annual spawning success at Yichang on the Yangtze River, 1996–2004, before and just after the Three Gorges Dam began operation. Captured were 96 875 ELS (early life stages: eggs, yolk-sac larvae = eleuthero embryos, and larvae); most were eggs and only 2477 were yolk-sac larvae. Most ELS were captured in the main river channel and inside the bend at the Yichang spawning reach. Yolk-sac larvae were captured for a maximum of 3 days after hatching began, indicating quick dispersal downstream. The back-calculated day of egg fertilization over the eight years indicated a maximum spawning window of 23 days (20 October–10 November). Spawning in all years was restricted temporally, occurred mostly at night and during one or two spawning periods, each lasting several days. The brief temporal spawning window may reduce egg predation by opportunistic predators by flooding the river bottom with millions of eggs. During 1996–2002, the percentage of fertilized eggs in an annual 20-egg sample was between 63.5 to 94.1%; however, in 2003 the percentage fertilized was only 23.8%. This sudden decline may be related to the altered environmental conditions at Yichang caused by operation of the Three Gorges Dam. Further studies are needed to monitor spawning and changes in egg fertilization in this threatened population.     

Cloning, expression and function of phosphate transporter encoded gene in Oryza sativa L.

OsPT6:1, a phosphate transporter encoding gene from the leaf samples of Oryza sativa, was identified through PCR with specifically designed primers. The phylogenetic analysis and the conserved amino acid residue site detection suggested OsPT6:1 a possible high-affinity phosphate transporter encoding gene. In situ hybridization and RT-PCR demonstrated the expression of OsPT6:1 in both roots and leaves. The peak expression signal was observed in mesophyll cells under low phosphorus (P) induction. A homologous recombination study indicated that OsPT6:1 can enhance the Pi uptake efficiency of Pichia pastoris. At the meantime, the introduction of OsPT6:1 was able to complement the Pi uptake function of yeast cells with high-affinity phosphate transporters deficient. Those results substantiated our contention that OsPT6:1 encoded a high-affinity phosphate transporter of Oryza sativa. These authors contributed equally to this work.     

Dynamic modification of cortical orientation tuning mediated by recurrent connections

Receptive field properties of visual cortical neurons depend on the spatiotemporal context within which the stimuli are presented. We have examined the temporal context dependence of cortical orientation tuning using dynamic visual stimuli with rapidly changing orientations. We found that tuning to the orientation of the test stimulus depended on a briefly presented preceding stimulus, with the preferred orientation shifting away from the preceding orientation. Analyses of the spatial-phase dependence of the shift showed that the effect cannot be explained by purely feedforward mechanisms, but can be accounted for by activity-dependent changes in the recurrent interactions between different orientation columns. Thus, short-term plasticity of the intracortical circuit can mediate dynamic modification of orientation tuning, which may be important for efficient visual coding.     

红壤茶树根层土壤基础呼吸作用和酶活性

对不同树龄茶树根层土壤的呼吸作用(包括代谢熵qCO2)和土壤酶(脲酶、转化酶和酸性磷酸单酯酶)活性进行了研究、不同树龄茶树根层土壤日基础呼吸作用强度(36．23—58．52mg·kg^-1·d^-1)和日代谢墒(0．30一0．68)都以40和90年茶树较为接近,分别显著大于和小于10年树龄茶树根层土壤;服酶活性(41．48—47、72mg·kg^-1·d^-1)则三者间差异不大,虽然随树龄增长而下降;转化酶活性(189．29—363．40mg·kg^-1·d^-1)也随树龄增长而下降,并且10年茶树根层土壤显著大于40和90年树龄茶树;而酸性磷酸单酯酶活性(444．22—828．32mg·kg^-1·d^-1)相反,随树龄增长而增强．结果表明,土壤基础呼吸作用、代谢熵和3种土壤酶活性都与茶树树龄、土壤pH、土壤有机碳、土壤全氮、土壤可活性酚总量、及土壤微生物生物量密切相关．