[On the role of liver-enriched transcription factors in regulating HBV transcription and replication].
OBJECTIVE
To investigate the effects of various liver-enriched transcription factors in regulating HBV transcription and replication, and to explore their potential roles in HBV hepatotropism.


METHODS
The replication-competent HBV recombinant plasmid pHBV4.1 plus different liver-enriched transcription factor (HNF1, HNF3, HNF4, HNF6, C/EBP and RXRa/PPARa) expression plasmids were co-transfected into nonhepatic cell lines (NIH3T3, HeLa, 293T, SW1353, CV-1 and COS1). The transcription levels of 3.5 kb, 2.4/2.1 kb and 0.7 kb HBV RNA were analyzed by Northern blot hybridization, and the level of HBV DNA replication intermediates was detected by Southern blot hybridization analysis.


RESULTS
In the absence of co-transfected liver enriched transcription factor expression vectors, the 3.5 kb HBV RNA is not transcribed and HBV DNA replication is not detected after transfecting of NIH 3T3 cells with pHBV4.1. Expression of the liver-enriched transcription factor HNF4 or RXRalpha/PPARalpha, stimulates the transcription of 3.5 kb HBV RNA and the replication of HBV DNA. In contrast, expression of HNF1, HNF3, HNF6 and C/EBP does not stimulate the transcription of 3.5 kb HBV RNA and therefore does not activate viral replication. HNF4 and RXRalpha/PPARalpha were also shown to activate the transcription of 3.5 kb HBV RNA and viral replication in divers cell types including HeLa, 293T, SW1353, CV-1 and COS1 cells. Mutation of the proximal nucleocapsid HNF4 binding site results in a greatly decreased level of HNF4 or RXRalpha/PPARalpha dependent HBV replication.


CONCLUSIONS
This study demonstrated that the liver-enriched transcription factors HNF4 and RXRa/PPARa can support HBV transcription and replication in nonhepatic cells, indicating that liver-specific gene transcription is one of the determinants of HBV hepatotropism.
Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
Song
S
Wang
Hong
H
Tang
Fang
F
He
Li
L
Liu
Fei-jun
FJ
Huang
Tao-you
TY
Zhou
Lian-san
LS
Zhao
D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D006515:Hepatitis B virus / Q000235:genetics* / Q000254:growth & development; D051537:Hepatocyte Nuclear Factor 1 / Q000235:genetics / Q000502:physiology; D051542:Hepatocyte Nuclear Factor 3-beta / Q000235:genetics / Q000502:physiology; D051557:Hepatocyte Nuclear Factor 4 / Q000235:genetics / Q000502:physiology; D051536:Hepatocyte Nuclear Factors / Q000235:genetics / Q000502:physiology; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic; D014162:Transfection; D014779:Virus Replication
D051557:Hepatocyte Nuclear Factor 4; D051536:Hepatocyte Nuclear Factors; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051542:Hepatocyte Nuclear Factor 3-beta