| Virus Name | Hepatitis B virus |
| Virus Short Name | HBV |
| Order | Unassigned |
| Virus Family | Hepadnaviridae |
| Virus Subfamily | N.A. |
| Genus | Orthohepadnavirus |
| Species | Hepatitis B virus |
| Host | Human, mammals |
| Cell Tropism | Hepatocytes |
| Associated Disease | Hepatitis, hepatocellular carcinoma(chronic infections), cirrhosis |
| Mode of Transmission | Sexual contact, blood, maternal-neonatal |
| VIPR DB link | N.A. |
| ICTV DB link | https://talk.ictvonline.org/ictv-reports/ictv_9th_report/reverse-transcribing-dna-and-rna-viruses-2011/w/rt_viruses/155/hepadnaviridae |
| Virus Host DB link | N.A. |
| Paper Title | SREBP-1a activation by HBx and the effect on hepatitis B virus enhancer II/core promoter |
| Author's Name | Ling Qiao, Qi Wu, Xinya Lu, Yan Zhou, Ana Fernandez-Alvarez, Lihong Ye, Xiaodong Zhang, Jihong Han, Marta Casado, Qiang Liu |
| Journal Name | Biochemical and Biophysical Research Communications |
| Pubmed ID | 23422505 |
| Abstract | Hepatitis B virus (HBV) X protein (HBx) plays an important role in HBV pathogenesis by regulating gene expression. Sterol regulatory element binding protein-1a (SREBP-1a) is a key transcriptional factor for modulating fatty acid and cholesterol synthesis. Here we demonstrated that HBx increased mature SREBP-1a protein level in the nucleus and its activity as a transcription factor. We further showed that the up-regulation of SREBP-1a by HBx occurred at the transcriptional level after ectopic expression and in the context of HBV replication. Deletional analysis using SREBP-1a promoter revealed that the sequence from -436 to -398 in the promoter was required for its activation by HBx. This promoter region possesses the binding sequences for two basic leucine zipper (b-ZIP) transcription factors, namely C/EBP and E4BP4. Mutagenesis of the binding sequences on the SREBP-1a promoter and ectopic expression experiments demonstrated that C/EBPalpha enhanced SREBP-1a activation by HBx, while E4BP4 had an inhibitory effect. C/EBPalpha was able to significantly reverse the inhibitory activity of E4BP4 on SREBP-1a promoter. These results demonstrated that HBx activates SREBP-1a activity at the transcription level through a complex mechanism involving two bZIP transcription factors C/EBP and E4BP4 with C/EBP being the dominant positive factor. Finally, we showed that knocking down SREBP-1 abolishes HBV enhancer II/core promoter activation by HBx. |
| Used Model | Huh-7 cells |
| DOI | 10.1016/j.bbrc.2013.02.030 |
