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[Study of HBV X protein and RMP, an RPB5 mediate protein competitively interacting with general transcription factor
1Department of Infectious Diseases, First Affiliated Hospital, Zhejiang Medical University, Hangzhou 310003, China.
Objective:
HBX is an essential viral protein that is important for HBV replication and might be a cofactor in the development of hepatocellular carcinoma. So many researchers are trying to find out the antagonistic factors of HBX. RMP, a newly cloned RNA polymerase II subunit RPB5 mediate protein, represses the transcription transactivation of HBV X protein. The purpose of this study was to elucidate the mechanism how RMP represses the transactivation of HBX.
Methods:
In this report, DNA recombinant technique in vitro protein-protein binding assay (Pull-Down assay) and chloramphenicol acetyltransferase assay were used.
Results:
The d10 domain of TF2B are responsible for binding to RMP, which is same as TF2B binding to the HBX protein. RMP specifically disrupts the binding between TF2B and HBX protein, vice versa HBX protein also disrupt the interaction of TF2B-RMP as demonstrated by the in vitro protein binding competition assay. Overexpression of RMP represses HBX transactivation on the reporters with HBX responsive cis-elements in transient transfected COS-1 cells. The repression can be rescued by overexpression of TF2B.
Conclusion:
The results clearly suggested that transcription co-activator HBX protein and corepressor RMP competitively associated with TF2B. Disrupting the interaction between transcription co-repressor RMP with TF2B is probably one of the mechanisms to account for the transcriptional transactivation of HBX protein.