The Activity of SV40 Promoter Can Be Inhibited by Overexpression of Heme Oxygenase-1 in Tumor Cells

E3 ubiquitin ligase Nedd4 inhibits AP-1 activity and TNF-α production through targeting p38α for polyubiquitination and subsequent degradation

p38α plays an important role in many inflammatory diseases, such as skin inflammation, endotoxic shock and arthritis. Ubiquitination is a vital posttranslational modification of proteins and plays a crucial regulatory role in inflammatory cells. It has been reported that ubiquitination of Tak1 and TAB1 upstream of p38α can regulate p38α activation respectively. However, p38α ubiquitination is not yet clear. In this paper, we showed that E3 ubiquitin ligase Nedd4 is a regulatory component of the p38α pathway and is responsible for polyubiquitination of p38α through K48-linked and K63-linked polyubiquitination. The levels of p38α and its downstream target TNF-α were increased in Nedd4 deficient macrophages response to LPS compared with wild-type cells. AP-1 activity and degradation of p38α were induced by Nedd4 in a dose-dependent manner. Furthermore, we found that phosphorylation of p38α is involved in the interactions between p38α and Nedd4 and subsequently promotes polyubiquitination of p38α, especially K48-linked polyubiquitination by Nedd4. The different conformation of two p38α isoforms (p38αV1 and p38αV2) might be the cause of their different interactions with Nedd4 and their polyubiquitination sites by Nedd4. Thus, NEDD4 is a previously unknown component of the p38α signaling complex necessary for TNF-α activation.

Two epitopes responsible for the catalytic activity of heme oxygenase-1 identified by phage display

Heme oxygenase‐1 (HO‐1) catalyzes the oxidative degradation of heme. The catalytic mechanism of the HO‐1 reaction has been determined gradually by studies of its crystal structure and HO‐1 mutants. However, the neutralizing epitopes responsible for HO‐1 activity remain elusive. Screening of a phage display library revealed four epitopes that could interact with the polyclonal antibody prepared by immunizing rabbits with the purified HO‐1 protein. Two of these four epitopes are responsible for HO‐1 catalytic activity because their antibodies were able to neutralize HO‐1 activity. The results of the present study shed further light on the molecular character of HO‐1.

Transcriptional activity assessment of three different promoters for mouse in utero electroporation system

In utero electroporation (IUE) is a simple and rapid approach to in vivo investigate exogenous gene function in mouse brain, and intensive studies using IUE have greatly contributed to analyze the characterization of specific steps during mouse brain development. Because the efficiency of IUE is highly dependent on the plasmid used and its concentration, and the transcriptional activity of plasmid is not only regulated by the host defense system, but also by the promoter of the expression vectors. Therefore, in the present study, we evaluated the transcriptional activity of three commonly used promoters, CMV, CAG and SV40, in IUE system through measuring the fluorescence intensity of green fluorescent protein which serves as an indicator. Our results demonstrated that the artificially-designed CAG promoter is a potent promoter that effectively drives target gene expression in IUE system.