l I. Therefore, efficient binding of UBF to rRNA gene is a pre-requisite for formation and assembly of initiation complex \[[@CR8]-[@CR10]\]. In mammalian cells, the UBF gene expression is regulated at both transcriptional and post-transcriptional levels. During development and differentiation, a diminished expression of UBF positively correlates with decreased rRNA synthesis while the cell cycle-dependent rRNA synthesis is primarily regulated through post-translational modifications of UBF \[[@CR8],[@CR11]\]. Not surprisingly, the intracellular level of UBF is a key determinant of active rRNA genes \[[@CR11]\]. Despite a critical role played by UBF in ribosome biogenesis, nothing much is known about the regulation of UBF gene expression except for the involvement of some growth regulators such as EGF, IGF and c-Myc in the process \[[@CR12]-[@CR16]\].

Taking into consideration, the complex interplay between ribosome biogenesis and neoplastic transformations, it is not surprising to observe the altered levels of UBF in many cancers such as breast and hepatic cancers \[[@CR17],[@CR18]\]. Importantly, elevated levels of UBF have also been reported in some HCC patients \[[@CR18]\]. Since the HBx oncoprotein of HBV is the major causative agent in the development of HCC, we wondered if UBF expression and activity was essential for hepatocarcinogenesis.

In the present study, we show that HBx can stimulate the expression of UBF gene with the help of transcription factor c-Myc. Further, UBF expression was essential for enhanced cell proliferation and transformation under the HBx microenvironment.

Results {#Sec2}
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HBx induces the expression of UBF in hepatic cell lines {#Sec3}
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Deregulation of UBF levels is frequently seen in cases of HCC \[[@CR18]\]. Therefore, the role of HBx in development of HCC was investigated under HBx microenvironment. The role of HBx in UBF expression was investigated after transiently transfecting Huh7 and IHH cells with either ve