Screening of hepatocyte proteins binding with C-terminally truncated surface antigen middle protein of hepatitis B virus (MHBst(167)) by a yeast two-hybrid system

The function of middle hepatitis B surface protein C-terminally truncated at amino acid position 167 (MHBst(167)) is not currently clear. This study aimed to screen and identify the proteins that interact with MHBst(167) in hepatocytes using a yeast two-hybrid system, and to explore the effects of MHBst(167) in the development of hepatocellular carcinoma and precancerous diseases of the liver. The MHBst(167) gene was amplified by polymerase chain reaction (PCR) and cloned into a pGEM-T vector. The target region was sequenced and the constructed bait plasmid, pGBKT7-MHBst(167), was transformed into AH109 yeast cells. The transformed AH109 cells were then mated with Y187 yeast cells containing the fetal liver cDNA library plasmid using a yeast two-hybrid system. The false positives were eliminated and the true positive clones were selected by PCR and sequencing analysis. The pGBKT7-MHBst(167) bait plasmid was successfully constructed and 66 clones grew in the selective synthetic defined media lacking leucine, tryptophan, histidine and adenine. Fifty-two clones were identified following X-α-Gal selection and segregation analysis. Seven proteins were found to be expressed that could interact with MHBst(167) in hepatocytes by the yeast two-hybrid system. These results have provided novel insights into the biological functions of MHBst(167).