NF-κB regulates the expression of STING via alternative promoter usage.

AIMS: Stimulator of interferon genes (STING) is a transmembrane protein in endoplasmic reticulum and plays crucial roles in autophagy, antiviral and anti-tumor responses. However, there are few studies on the transcriptional regulation mechanism of STING. MAIN METHODS: The 5' RACE experiment was used to determine the location of STING promoters. Luciferase reporting assay confirmed the activity and core region of STING internal promoter. Site-directed mutagenesis confirmed that NF-κB regulates the activity of STING promoters. The regulation of NF-κB on STING was investigated by real-time quantitative PCR, western blot, chromatin immunoprecipitation assay and lipopolysaccharide (LPS) inflammatory cell model. KEY FINDINGS: There was also a transcription start site at the 17 bp sequence upstream of STING second exon. STING-285 was the core region of the internal promoter. After NF-κB binding site mutation, the activity of STING internal promoter decreased significantly. In addition, we found that NF-κB can bind to the promoter region of wild-type STING. Overexpression of NF-κB significantly increased the activity of STING internal promoter and wild-type promoter, while knockdown of endogenous NF-κB significantly inhibited the activity of STING promoters. The binding of NF-κB to STING promoters in vivo were confirmed by chromatin immunoprecipitation assay. Meanwhile, we stimulated HeLa cells with LPS to activate the NF-κB pathway and found that STING expression was up-regulated. SIGNIFICANCE: These results suggest that transcription factor NF-κB positively regulates the expression of STING via alternative promoter usage. This provides a new basis and potential drug targets for the clinical treatment of STING related diseases.

Hepatitis D: challenges in the estimation of true prevalence and laboratory diagnosis.

Hepatitis delta virus (HDV) is a defective single negative chain RNA virus, as its envelope protein synthesis is dependent on hepatitis B virus (HBV). Studies have consistently shown that coinfection of HBV and HDV is the most serious form of viral hepatitis, with accelerated progression to liver cirrhosis and hepatocellular carcinoma. About 74 million of HBV surface antigen (HBsAg) positive patients worldwide are also co-infected with HDV. Besides, patients with intravenous drug use and high-risk sexual behavior are at higher risk of HDV infection. Therapeutic schedules for HDV are limited, and relapse of HDV has been observed after treatment with pegylated interferon alpha. To reduce the transmission of HDV, all people infected with HBV should be screened for HDV. At present, several serological and molecular detection methods are widely used in the diagnosis of HDV. However, due to the lack of international standards diagnostic results from different laboratories are often not comparable. Therefore, the true prevalence of HDV is still unclear. In this manuscript, we have analyzed various factors influencing the estimation of HDV prevalence. We have also discussed about the advantages and disadvantages of currently available HDV laboratory diagnostic methods, in order to provide some ideas for improving the detection of HDV.

Transcriptional regulation of human cyclic GMP-AMP synthase gene.

Cyclic GMP-AMP synthase (cGAS, cGAMP synthase) plays crucial roles in autoimmune disease, anti-tumor response, anti-senescence and anti-inflammatory response. Many studies have focused on cGAS-mediated signaling pathway. However, transcriptional mechanisms of cGAS gene have remained largely unknown. Here, we cloned the cGAS promoter region and characterized the molecular mechanisms controlling the cGAS transcriptional activity. By a series of 5' deletion and promoter constructions, we showed that the region (-414 to +76 relatives to the transcription start site) was sufficient for promoter activity. Mutation of Sp1 and CREB binding sites in this promoter region led to an apparent reduction of the cGAS promoter activity. Overexpression of Sp1 and CREB could obviously enhance promoter activity, whereas knocking-down of endogenous Sp1 and CREB markedly restrained the cGAS promoter activity. Sp1 and CREB binding to the cGAS promoter region in vivo was verified by Chromatin immunoprecipitation assay. These results pointed out that transcription factors Sp1 and CREB regulate the transcription of the cGAS gene.