Hepatitis B virus X protein induces CRT transcription by activating C/EBPα / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the molecular mechanism of calreticulin ( CRT) transcription induced by HBV and its viral proteins. Methods The human hepatocellular cell line, HepG2, was trans-fected with pHBV1. 3 and eukaryotic expression plasmids of HBV viral proteins, respectively. The expres-sion of CRT was measured after transfection. A reporter plasmid of CRT promoter was constructed to analyze the induction of CRT promoter by pHBV1. 3 and HBV viral proteins. Furthermore, two truncated and one C/EBPα site deficient mutants were constructed to evaluate the regulatory effects of HBx on CRT promoter. Fi-nally, HepG2 cells were transfected with HBx expression plasmids and the cellular localization of C/EBPαwas analyzed. Results In this study, pHBV1. 3 could significantly up-regulate the expression of CRT at mRNA and protein levels as well as enhancing the activity of CRT promoter. Among the seven HBV viral proteins, HBx could enhance the activity of CRT promoter and the expression of CRT at mRNA and protein levels. HBx could not induce the transcription of CRT when the C/EBPα binding site was deleted from the CRT promoter. The expression of HBx could promote the nuclear translocation of C/EBPα. Conclusion HBV and its viral protein HBx could up-regulate the CRT expression at transcriptional level. The transcrip-tional factor C/EBPα played a critical role in HBx-induced transcriptional activation of CRT.