Transcriptional regulation of the TFIIH transcription repair components XPB and XPD by the hepatitis B virus x protein in liver cells and transgenic liver tissue.
Human hepatitis B virus is a risk factor for the development of hepatocellular carcinoma. The hepatitis B virus x protein (HBx) has been shown to inactivate the p53 tumor suppressor protein and impair DNA repair, cell cycle, and apoptosis mechanisms. Herein we report that HBx represses two components of the transcription-repair factor TFIIH, XPB (p89), and XPD (p80), both in p53-proficient and p53-deficient liver cells. This inhibition is observed while HBx maintains its transactivation function. Expression of HBx in liver cells results in down-regulation of endogenous XPB and XPD mRNAs and proteins; this inhibition is not observed with other TFIIH subunits, XPA or PCNA. In liver tissue from HBx transgenics, XPB and XPD proteins are down-regulated in comparison to matched normal liver tissue. HBx has been shown to interact with Sp1 transcription factor and affects its DNA binding activity. Sp1 is essential for the basal promoter activity of XPB in liver cells and Drosophila SL2 cells. In the Sp1-deficient SL2 cells, HBx-induced XPB and XPD inhibition is Sp1-dependent. In summary, our results provide evidence that HBx represses the expression of key TFIIH proteins at least in part through Sp1 elements; this repression may impair TFIIH function in DNA repair mechanisms.
Lady Davis Institute of the Sir Mortimer B. Davis Jewish General Hospital, Departments of Medicine, Pharmacology and Therapeutics, Pathology, and Oncology, Faculty of Medicine, McGill University, Montreal H3T 1E2, Canada.
I
I
Jaitovich-Groisman
N
N
Benlimame
B L
BL
Slagle
M H
MH
Perez
L
L
Alpert
D J
DJ
Song
N
N
Fotouhi-Ardakani
J
J
Galipeau
M A
MA
Alaoui-Jamali
D000818:Animals; D030801:Animals, Genetically Modified; D017209:Apoptosis; D015153:Blotting, Western; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D004265:DNA Helicases; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation; D004330:Drosophila; D029721:Drosophila Proteins; D005260:Female; D005434:Flow Cytometry; D015967:Gene Expression Regulation, Viral; D006801:Humans; D007150:Immunohistochemistry; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008957:Models, Genetic; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D035381:TATA-Binding Protein Associated Factors; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism*; D035362:Transcription Factor TFIID; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000235:genetics*; D019473:Transcription Factors, TFII; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D054334:Viral Regulatory and Accessory Proteins; D051759:Xeroderma Pigmentosum Group D Protein
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D011506:Proteins; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D035381:TATA-Binding Protein Associated Factors; C084976:Taf6 protein, Drosophila; D015534:Trans-Activators; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; C072022:XPBC-ERCC-3 protein; D051758:Transcription Factor TFIIH; D015500:Chloramphenicol O-Acetyltransferase; D004265:DNA Helicases; D051759:Xeroderma Pigmentosum Group D Protein; C497292:ERCC2 protein, human; C497293:Ercc2 protein, mouse