N. Kuzhandaivelu et al., XAP2, A NOVEL HEPATITIS-B VIRUS X-ASSOCIATED PROTEIN THAT INHIBITS X TRANSACTIVATION, Nucleic acids research, 24(23), 1996, pp. 4741-4750
The hepatitis B virus X protein is a promiscuous transcriptional trans
activator, Transactivation by the X protein is most likely mediated th
rough binding to different cellular factors, Using the yeast two-hybri
d method, we have isolated a clone that encodes a novel X-associated c
ellular protein XAP2. X and XAP2 interactions also occur in vitro. Ant
iserum raised against XAP2 recognizes a cytoplasmic protein with an ap
parent molecular mass of 36 kDa. The interaction between X and XAP2 re
quires a small region on X containing amino acids 13-26. From Northern
blot analyses, XAP2 is ubiquitously expressed in both liver-derived a
nd 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 trans
activation by the X protein, Based on these results, we suggest that X
AP2 is an important cellular negative regulator of the X protein, and
that X-XAP2 interaction may play a role in HBV pathology.