Ribavirin-induced intracellular GTP depletion activates transcription elongation in coagulation factor VII gene expression.
Coagulation FVII (Factor VII) is a vitamin K-dependent glycoprotein synthesized in hepatocytes. It was reported previously that FVII gene (F7) expression was up-regulated by ribavirin treatment in hepatitis C virus-infected haemophilia patients; however, its precise mechanism is still unknown. In the present study, we investigated the molecular mechanism of ribavirin-induced up-regulation of F7 expression in HepG2 (human hepatoma cell line). We found that intracellular GTP depletion by ribavirin as well as other IMPDH (inosine-5'-monophosphate dehydrogenase) inhibitors, such as mycophenolic acid and 6-mercaptopurine, up-regulated F7 expression. FVII mRNA transcription was mainly enhanced by accelerated transcription elongation, which was mediated by the P-TEFb (positive-transcription elongation factor b) complex, rather than by promoter activation. Ribavirin unregulated ELL (eleven-nineteen lysine-rich leukaemia) 3 mRNA expression before F7 up-regulation. We observed that ribavirin enhanced ELL3 recruitment to F7, whereas knockdown of ELL3 diminished ribavirin-induced FVII mRNA up-regulation. Ribavirin also enhanced recruitment of CDK9 (cyclin-dependent kinase 9) and AFF4 to F7. These data suggest that ribavirin-induced intracellular GTP depletion recruits a super elongation complex containing P-TEFb, AFF4 and ELL3, to F7, and modulates FVII mRNA transcription elongation. Collectively, we have elucidated a basal mechanism for ribavirin-induced FVII mRNA up-regulation by acceleration of transcription elongation, which may be crucial in understanding its pleiotropic functions in vivo.
Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya 461-8673, Japan.
Atsuo
A
Suzuki
Yuhri
Y
Miyawaki
Eriko
E
Okuyama
Moe
M
Murata
Yumi
Y
Ando
Io
I
Kato
Yuki
Y
Takagi
Akira
A
Takagi
Takashi
T
Murate
Hidehiko
H
Saito
Tetsuhito
T
Kojima
D000963:Antimetabolites / Q000494:pharmacology*; D005167:Factor VII / Q000096:biosynthesis / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D006160:Guanosine Triphosphate / Q000037:antagonists & inhibitors / Q000172:deficiency*; D056945:Hep G2 Cells; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism*; D012254:Ribavirin / Q000494:pharmacology*; D061805:Transcription Elongation, Genetic / Q000187:drug effects / Q000502:physiology*
D000963:Antimetabolites; D012254:Ribavirin; D006160:Guanosine Triphosphate; D005167:Factor VII