IL-1β/ATF3-mediated induction of Ski2 expression enhances hepatitis B virus x mRNA degradation.

Hepatitis B virus (HBV) -x protein is a transcriptional regulator required for the HBV life cycle. HBx also induces complications in the host such as hepatocellular carcinoma. We previously showed that HBx mRNA is degraded by the Ski2/RNA exosome complex. In the present study, we report the regulation of this system through the control of Ski2 expression. We identified interleukin (IL) -1β as an inducer of expression from the Ski2 promoter. IL-1β induced the expression of ATF3 transcription factor, which in turn binds to cyclic AMP-responsive element sequence in the Ski2 promoter and is responsible for Ski2 promoter induction by IL-1β. We previously reported that Ski2 expression increases HBx mRNA degradation; consistent with those data, we showed here that HBx mRNA is degraded in response to IL-1β treatment. Interestingly, HBx also significantly induced Ski2 expression. To our knowledge, this is the first report to show activation of the Ski2/RNA exosome complex by both the host and HBV. Understanding the regulation of the Ski2/RNA exosome system is expected to facilitate prevention of HBx-mediated complications through targeting the posttranscriptional degradation of HBx mRNA; and will also help shedding a light on the role of RNA decay systems in inflammation.