A novel hepatitis B virus X-interactive protein: cytochrome C oxidase III.
BACKGROUND
Hepatitis B virus-encoded X protein has been shown to be capable of activating many different viral and cellular promoters through protein-protein interactions and to contribute to the development of hepatocellular carcinoma. As its mechanism has not yet been identified unequivocally, the aim of the present study was to screen the cellular proteins that can interact with X protein.


METHODS
The yeast two-hybrid system was used to screen the X-interactive protein. False positive clones were eliminated by segregation analysis, and then putative positive clones were amplified, sequenced and analyzed with bioinformatics. A mating experiment was performed to confirm the binding of putative proteins to X protein in the yeast cells. The specific interaction between X protein and putative proteins in mammalian cells was verified by coimmunoprecipitation.


RESULTS
The hepatitis B virus X-interactive protein recovered from a human liver cDNA library was cytochrome C oxidase III. The specific interaction between protein X and cytochrome C oxidase III was verified by mating experiment and coimmunoprecipitation of COS7 cell lysates expressing both proteins.


CONCLUSIONS
These data support the speculation that cytochrome C oxidase III is a novel functional target of hepatitis B virus X protein in cells.
Wang
Xiao Zhong
XZ
Department of Gastroenterology, Union Hospital of Fujian Medical University, Fuzhou, Fujian Province, China. drwangxz@pub6.fz.fj.cn
Li
Dan
D
Tao
Qi Min
QM
Lin
Na
N
Chen
Zhi Xin
ZX