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As a major diarrheagenic human pathogen, enterohemorrhagic Escherichia coli (EHEC) produce attaching and effacing (A/E) lesions, characterized by the formation of actin pedestals, on mammalian cells. A bacterial T3SS effector NleL from EHEC O157:H7 was recently shown to be a HECT-like E3 ligase in vitro, but its biological functions and host targets remain elusive. Here, we report that NleL is required to effectively promote EHEC-induced A/E lesions and bacterial infection. Furthermore, human c-Jun NH2-terminal kinases (JNKs) were identified as primary substrates of NleL. NleL-induced JNK ubiquitylation, particularly mono-ubiquitylation at the Lys 68 residue of JNK, impairs JNK’s interaction with an upstream kinase MKK7, thus disrupting JNK phosphorylation and activation. This subsequently suppresses the transcriptional activity of activator protein-1 (AP-1), which modulates the formation of the EHEC-induced actin pedestals. Moreover, JNK knockdown or inhibition in host cells complements NleL deficiency in EHEC infection. Thus, we demonstrate that the effector protein NleL enhances the ability of EHEC to infect host cells by targeting host JNK, and elucidate an inhibitory role of ubiquitylation in regulating JNK phosphorylation.

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With in‐situ bending various contents of nano‐sized titanium dioxide (TiO2) were introduced into the solution polymerization system of poly (p‐phenylene benzobisoxazole) (PBO), and the blends were spun into high performance fibers via liquid crystal spinning. The dispersion of TiO2 in matrix was observed by the scanning electron microscopy. The mechanical and thermal properties of PBO and TiO2/PBO fibers were tested by a tensilon and a thermogravimetric analyser. The results show that the tensile strength and modulus of the PBO/TiO2 fiber containing 1.5 wt % TiO2 is 4.62 GPa and 109.99 GPa, which is approximately 36% and 18% higher than that of the pure PBO fiber. The decomposition temperature of the composites is also improved from 697.6°C to 701.8°C. The effect of TiO2 nanoparticles on the structure of PBO is also studied. Copyright © 2009 John Wiley & Sons, Ltd.