Mesophyll specific expression of a bacterial mercury transporter-based vacuolar sequestration machinery sufficiently enhances mercury tolerance of Arabidopsis.

We aimed to efficiently enhance plant Hg(II) tolerance by the transgenic approach utilizing a bacterial mercury transporter MerC, an Arabidopsis mesophyll specific promoter pRBCS1A, and a vacuolar membrane targeting syntaxin AtVAM3/SYP22. We generated two independent homozygous Arabidopsis pRBCS1A-TCV lines expressing mT-Sapphire-MerC-AtVAM3 under the control of pRBCS1A. Quantitative RT-PCR showed that the transgene was expressed specifically in shoots of pRBCS1A-TCV lines. Confocal analyses further demonstrated the leaf mesophyll specific expression of mT-Sapphire-MerC-AtVAM3. Confocal observation of the protoplast derived from the F1 plants of the pRBCS1A-TCV line and the tonoplast marker line p35S-GFP-δTIP showed the tonoplast colocalization of mT-Sapphire-MerC-AtVAM3 and GFP-δTIP. These results clearly demonstrated that mT-Sapphire-MerC-AtVAM3 expression in Arabidopsis is spatially regulated as designed at the transcript and the membrane trafficking levels. We then examined the Hg(II) tolerance of the pRBCS1A-TCV lines as well as the p35S-driven MerC-AtVAM3 expressing line p35S-CV under the various Hg(II) stress conditions. Short-term (12 d) Hg(II) treatment indicated the enhanced Hg(II) tolerance of both pRBCS1A-TCV and p35S-CV lines. The longer (3 weeks) Hg(II) treatment highlighted the better shoot growth of the transgenic plants compared to the wild-type Col-0 and the pRBCS1A-TCV lines were more tolerant to Hg(II) stress than the p35S-CV line. These results suggest that mesophyll-specific expression of MerC-AtVAM3 is sufficient or even better to enhance the Arabidopsis Hg(II) tolerance. The Hg accumulation in roots and shoots did not differ between the wild-type Col-0 and the MerC-AtVAM3 expressing plants, suggesting that the boosted Hg(II) tolerance of the transgenic lines would be attributed to vacuolar Hg-sequestration by the tonoplast-localized MerC. Further perspectives of the MerC-based plant engineering are also discussed.

Wheat germ cell-free system-based production of hemagglutinin-neuraminidase glycoprotein of human parainfluenza virus type 3 for generation and characterization of monoclonal antibody.

Human parainfluenza virus 3 (HPIV3) commonly causes respiratory disorders in infants and young children. Monoclonal antibodies (MAbs) have been produced to several components of HPIV3 and commercially available. However, the utility of these antibodies for several immunological and proteomic assays for understanding the nature of HPIV3 infection remain to be characterized. Herein, we report the development and characterization of MAbs against hemagglutinin-neuraminidase (HN) of HPIV3. A recombinant full-length HPIV3-HN was successfully synthesized using the wheat-germ cell-free protein production system. After immunization and cell fusion, 36 mouse hybridomas producing MAbs to HPIV3-HN were established. The MAbs obtained were fully characterized using ELISA, immunoblotting, and immunofluorescent analyses. Of the MAbs tested, single clone was found to be applicable in both flow cytometry and immunoprecipitation procedures. By utilizing the antibody, we identified HPIV3-HN binding host proteins via immunoprecipitation-based mass spectrometry analysis. The newly-developed MAbs could thus be a valuable tool for the study of HPIV3 infection as well as the several diagnostic tests of this virus.

The exon-junction complex proteins, Y14 and MAGOH regulate STAT3 activation.

Signal transducer and activator of transcription 3 (STAT3), which is activated by cytokines and growth factors, mediates biological actions in many physiological processes. In a previous study, we found that Y14, a core component of the exon-junction complex (EJC) bound to STAT3 and upregulated the transcriptional activity of STAT3 by influencing its DNA-binding activity. In the present study, we demonstrate that STAT3 endogenously interacts with Y14. In addition, we found that MAGOH, a Y14 partner in the EJC, inhibits the STAT3-Y14 complex formation. Furthermore, small-interfering RNA-mediated reduction of MAGOH expression enhanced interleukin-6-induced gene expression. These results indicate that MAGOH regulates the transcriptional activation of STAT3 by interfering complex formation between STAT3 and Y14.

HDAC3 influences phosphorylation of STAT3 at serine 727 by interacting with PP2A.

Signal transducer and activator of transcription 3 (STAT3), which mediates biological actions in many physiological processes, is activated by cytokines and growth factors, and has been reported to be involved in the pathogenesis of various human diseases. Here, we show that treatment of HeLa cells with a histone deacetylase (HDAC) inhibitor, trichostatin A, or small-interfering RNA (siRNA)-mediated repression of HDAC3, enhances phosphorylation of STAT3 at Ser727. Furthermore, dephosphorylation of STAT3 at Ser727 by protein phosphatase 2A (PP2A) was restored by treatment of cells with HDAC3 siRNA. We further found that formation of a complex between STAT3 and PP2A was enhanced in the presence of HDAC3. Importantly, small-interfering RNA-mediated repression of both HDAC3 and PP2A effectively enhanced leukemia inhibitory factor (LIF)-induced STAT3 activation. These results indicate that HDAC3 may act as a scaffold protein for PP2A to regulate the LIF/STAT3-mediated signaling pathway.

Physical and functional interactions between ZIP kinase and UbcH5.

Zipper-interacting protein kinase (ZIPK) is a widely expressed serine/threonine kinase that has been implicated in cell death and transcriptional regulation, but its mechanism of regulation remains unknown. In our previous study, we showed that leukemia inhibitory factor stimulated threonine-265 phosphorylation of ZIPK, thereby leading to phosphorylation and activation of signal transducer and activator of transcription 3. Here, we identified UbcH5c as a novel ZIPK-binding partner by yeast two-hybrid screening. Importantly, we found that UbcH5c induced ubiquitination of ZIPK. Small-interfering RNA-mediated reduction of endogenous UbcH5 expression decreased ZIPK ubiquitination. Furthermore, coexpression of UbcH5c with ZIPK influenced promyelocytic leukemia protein nuclear body (PML-NB) formation. These results suggest that UbcH5 regulates ZIPK accumulation in PML-NBs by interacting with ZIPK and stimulating its ubiquitination.

The IL-6 family of cytokines modulates STAT3 activation by desumoylation of PML through SENP1 induction.

Post-translational modification by small ubiquitin-like modifier (SUMO) plays an important role in the regulation of different signaling pathways and is involved in the formation of promyelocytic leukemia (PML) protein nuclear bodies following sumoylation of PML. In the present study, we found that IL-6 induces desumoylation of PML and dissociation between PML and SUMO1 in hepatoma cells. We also found that IL-6 induces mRNA expression of SENP1, a member of the SUMO-specific protease family. Furthermore, wild-type SENP1 but not an inactive SENP1 mutant restored the PML-mediated suppression of STAT3 activation. These results indicate that the IL-6 family of cytokines modulates STAT3 activation by desumoylation and inactivation PML through SENP1 induction.

An RNA biding protein, Y14 interacts with and modulates STAT3 activation.

Signal transducer and activator of transcription 3 (STAT3), which mediates biological actions in many physiological processes, is activated by cytokines and growth factors via specific tyrosine-phosphorylation, dimerization, and nuclear translocation. To clarify the molecular mechanisms underlying the regulation of STAT3 activation, we performed yeast two-hybrid screening. We identified Y14, an RNA-binding protein, as a novel STAT3 binding partner. Y14 bound to STAT3 through the C-terminal region of STAT3 in vivo. Importantly, small-interfering RNA-mediated reduction of endogenous Y14 expression decreased IL-6-induced tyrosine-phosphorylation, nuclear accumulation, and DNA-binding activity of STAT3, as well as IL-6/STAT3-dependent gene expression. These results indicate that Y14 interacts with STAT3 and regulates the transcriptional activation of STAT3 by influencing the tyrosine-phosphorylation of STAT3.