Related Experiment Videos
XAP2, a novel hepatitis B virus X-associated protein that inhibits X transactivation
N Kuzhandaivelu1, Y S Cong, C Inouye
1Moffitt Cancer Center and Research Institute, Department of Medical Microbiology and Immunology, University of South Florida, Tampa 33612, USA.
Abstract:
The hepatitis B virus X protein is a promiscuous transcriptional transactivator. Transactivation by the X protein is most likely mediated through binding to different cellular factors. Using the yeast two-hybrid method, we have isolated a clone that encodes a novel X-associated cellular protein: XAP2. X and XAP2 interactions also occur in vitro. Antiserum raised against XAP2 recognizes a cytoplasmic protein with an apparent molecular mass of 36 kDa. The interaction between X and XAP2 requires a small region on X containing amino acids 13-26. From Northern blot analyses, XAP2 is ubiquitously expressed in both liver-derived and non-liver-derived cell lines as well as in normal non-liver tissues. In contrast, XAP2 is expressed in very low level in the normal human liver. In transfection assays, overexpression of XAP2 abolishes transactivation by the X protein. Based on these results, we suggest that XAP2 is an important cellular negative regulator of the X protein, and that X-XAP2 interaction may play a role in HBV pathology.
Insights
Researchers identified XAP2, a novel protein interacting with the hepatitis B virus X protein. Overexpression of XAP2 inhibits X protein activity, suggesting XAP2 acts as a negative regulator in HBV infection.
Area of Science:
- Hepatology
- Virology
- Molecular Biology
Background:
- The hepatitis B virus (HBV) X protein (HBx) is a key viral factor involved in HBV pathogenesis.
- HBx functions as a promiscuous transcriptional transactivator, influencing numerous cellular processes.
- The precise mechanisms of HBx transactivation and its regulation by cellular factors are not fully understood.
Purpose of the Study:
- To identify novel cellular proteins that interact with the hepatitis B virus X protein.
- To characterize the functional role of a newly identified X protein-associated protein (XAP2) in regulating HBx activity.
- To investigate the potential involvement of the X-XAP2 interaction in HBV pathology.
Main Methods:
- Yeast two-hybrid screening was employed to identify cellular interacting partners of HBx.
- In vitro binding assays were performed to confirm the interaction between HBx and XAP2.
- Northern blot analysis was used to determine the expression pattern of XAP2 in various cell lines and tissues.
- Transfection assays were conducted to assess the effect of XAP2 overexpression on HBx-mediated transactivation.
Main Results:
- A novel cellular protein, designated XAP2, was identified as an interacting partner of the hepatitis B virus X protein.
- The interaction between HBx and XAP2 was confirmed both in yeast and in vitro, involving specific amino acids within HBx.
- XAP2 is ubiquitously expressed in non-liver tissues and cell lines but shows very low expression in normal human liver.
- Overexpression of XAP2 significantly inhibited the transactivation function of the hepatitis B virus X protein.
Conclusions:
- XAP2 is identified as a novel cellular protein that interacts with the hepatitis B virus X protein.
- XAP2 functions as a cellular negative regulator of HBx, diminishing its transactivation capability.
- The interaction between HBx and XAP2 may play a significant role in the pathogenesis of hepatitis B virus infection.