Ubiquitin-mediated proteolysis regulates the activity of diverse receptor systems. Here, we identify Smurf2, a C2-WW-HECT domain ubiquitin ligase and show that Smurf2 associates constitutively with Smad7. Smurf2 is nuclear, but binding to Smad7 induces export and recruitment to the activated TGF beta receptor, where it causes degradation of receptors and Smad7 via proteasomal and lysosomal pathways. IFN gamma, which stimulates expression of Smad7, induces Smad7-Smurf2 complex formation and increases TGF beta receptor turnover, which is stabilized by blocking Smad7 or Smurf2 expression. Furthermore, Smad7 mutants that interfere with recruitment of Smurf2 to the receptors are compromised in their inhibitory activity. These studies thus define Smad7 as an adaptor in an E3 ubiquitin-ligase complex that targets the TGF beta receptor for degradation.

The TGF-beta superfamily of proteins regulates many different biological processes, including cell growth, differentiation and embryonic pattern formation. TGF-beta-like factors signal across cell membranes through complexes of transmembrane receptors known as type I and type II serine/threonine-kinase receptors, which in turn activate the SMAD signalling pathway. On the inside of the cell membrane, a receptor-regulated class of SMADs are phosphorylated by the type-I-receptor kinase. In this way, receptors for different factors are able to pass on specific signals along the pathway: for example, receptors for bone morphogenetic protein (BMP) target SMADs 1, 5 and 8, whereas receptors for activin and TGF-beta target SMADs 2 and 3. Phosphorylation of receptor-regulated SMADs induces their association with Smad4, the 'common-partner' SMAD, and stimulates accumulation of this complex in the nucleus, where it regulates transcriptional responses. Here we describe Smurf1, a new member of the Hect family of E3 ubiquitin ligases. Smurf1 selectively interacts with receptor-regulated SMADs specific for the BMP pathway in order to trigger their ubiquitination and degradation, and hence their inactivation. In the amphibian Xenopus laevis, Smurf1 messenger RNA is localized to the animal pole of the egg; in Xenopus embryos, ectopic Smurf1 inhibits the transmission of BMP signals and thereby affects pattern formation. Smurf1 also enhances cellular responsiveness to the Smad2 (activin/TGF-beta) pathway. Thus, targeted ubiquitination of SMADs may serve to control both embryonic development and a wide variety of cellular responses to TGF-beta signals.

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Circulating microRNAs (miRNAs) were found to exist in serum/plasma in a highly stable, cell-free form, and aberrantly expressed in many human diseases. Currently, the expression levels of circulating miRNAs are estimated by quantitative real-time polymerase chain reaction. However, no study has systematically evaluated reference genes for evaluating circulating microRNA expression. This study describes the identification and characterization of an appropriate reference gene for the normalization of circulating miRNA levels in hepatitis B virus (HBV)-infected patients and healthy people. Ten miRNAs that resemble the mean expression of the TaqMan low density array together with U6, RNU6B, and miR-16 were validated with two algorithms, geNorm, and NormFinder, after ensuring their equivalent expression between the two study groups. The combination of miR-26a, miR-221, and miR-22* is recommended as the most stable set of reference genes for circulating miRNA evaluation in HBV patients and healthy people.

Several plant lipid transfer proteins (LTPs) act positively in plant disease resistance. Here, we show that LTP3 (At5g59320), a pathogen and abscisic acid (ABA)-induced gene, negatively regulates plant immunity in Arabidopsis. The overexpression of LTP3 (LTP3-OX) led to an enhanced susceptibility to virulent bacteria and compromised resistance to avirulent bacteria. On infection of LTP3-OX plants with Pseudomonas syringae pv. tomato, genes involved in ABA biosynthesis, NCED3 and AAO3, were highly induced, whereas salicylic acid (SA)-related genes, ICS1 and PR1, were down-regulated. Accordingly, in LTP3-OX plants, we observed increased ABA levels and decreased SA levels relative to the wild-type. We also showed that the LTP3 overexpression-mediated enhanced susceptibility was partially dependent on AAO3. Interestingly, loss of function of LTP3 (ltp3-1) did not affect ABA pathways, but resulted in PR1 gene induction and elevated SA levels, suggesting that LTP3 can negatively regulate SA in an ABA-independent manner. However, a double mutant consisting of ltp3-1 and silent LTP4 (ltp3/ltp4) showed reduced susceptibility to Pseudomonas and down-regulation of ABA biosynthesis genes, suggesting that LTP3 acts in a redundant manner with its closest homologue LTP4 by modulating the ABA pathway. Taken together, our data show that LTP3 is a novel negative regulator of plant immunity which acts through the manipulation of the ABA-SA balance.

Interferons (IFNs) are proteins produced by a variety of cells during the process of virus infection. It can activate the transcription of multiple functional genes in cells, regulate the synergistic effect of multiple signaling pathways, and mediate a variety of biological functions such as antiviral activity and immune regulation. The symptoms of hosts infected with African swine fever virus (ASFV) depend on the combined interaction between viruses and the host. However, it is unclear whether IFNs can be used as an emergency preventive treatment for ASFV. This study focused on the use of recombinant porcine IFNs, produced by Escherichia coli, to inhibit the replication of ASFV. The activity of IFN against ASFV was detected using primary alveolar macrophages at different doses through immunofluorescence assays and quantitative real-time PCR. We found that both 1000 and 100 U/mL doses significantly inhibited the replication of ASFV. Meanwhile, we found that IFNs could significantly trigger the production of a variety of IFN-induced genes (IFIT1, IFITM3, Mx-1, OASL, ISG15, PKR, GBP1, Viperin, BST2, IRF-1, and CXCL10) and MHC molecules, which play key roles in resistance to virus infection. Peripheral blood samples were also obtained from surviving pigs treated with IFNs, and the viral load was determined. Consistent with in vitro tests, low-dose (10 5 U/kg) recombinant porcine IFNs (PoIFN-α and PoIFN-γ) significantly reduced viral load compared to that with high-dose (10 6 U/kg) treatment. Our results suggest that recombinant porcine IFNs have high antiviral activity against ASFV, providing a new strategy for the prevention of African swine fever.

As the number of transgenic livestock increases, reliable detection and molecular characterization of transgene integration sites and copy number are crucial not only for interpreting the relationship between the integration site and the specific phenotype but also for commercial and economic demands. However, the ability of conventional PCR techniques to detect incomplete and multiple integration events is limited, making it technically challenging to characterize transgenes. Next-generation sequencing has enabled cost-effective, routine and widespread high-throughput genomic analysis. Here, we demonstrate the use of next-generation sequencing to extensively characterize cattle harboring a 150-kb human lactoferrin transgene that was initially analyzed by chromosome walking without success. Using this approach, the sites upstream and downstream of the target gene integration site in the host genome were identified at the single nucleotide level. The sequencing result was verified by event-specific PCR for the integration sites and FISH for the chromosomal location. Sequencing depth analysis revealed that multiple copies of the incomplete target gene and the vector backbone were present in the host genome. Upon integration, complex recombination was also observed between the target gene and the vector backbone. These findings indicate that next-generation sequencing is a reliable and accurate approach for the molecular characterization of the transgene sequence, integration sites and copy number in transgenic species.

Bacteria can change its lifestyle during inhabiting in host niches where they survive and replicate by rapidly altering gene expression pattern to accommodate the new environment. In this study, two novel regulators in avian pathogenic Escherichia coli (APEC) were identified and designated as AutA and AutR. RT-PCR and β-galactosidase assay results showed that AutA and AutR co-regulated the expression of adhesin UpaB in APEC strain DE205B. Electrophoretic mobility shift assay showed that AutA and AutR could directly bind the upaB promoter DNA. In vitro transcription assay indicated that AutA could activate the upaB transcription, while AutR inhibited the upaB transcription due to directly suppressing the activating effect of AutA on UpaB expression. Transcriptome analysis showed that AutA and AutR coherently affected the expression of hundreds of genes. Our study confirmed that AutA and AutR co-regulated the expression of DE205B K1 capsule and acid resistance systems in E. coli acid fitness island (AFI). Moreover, phenotypic heterogeneity in expression of K1 capsule and acid resistance systems in AFI during host–pathogen interaction was associated with the regulation of AutA and AutR. Collectively speaking, our studies presented that AutA and AutR are involved in APEC adaptive lifestyle change to facilitate its infection.