Hepatitis B virus X protein impedes the DNA repair via its association with transcription factor, TFIIH
1 NUST Center of Virology and Immunology, National University of Science and Technology, Academic Block, Kashmir Highway, H-12 Islamabad, Pakistan
2 Department of Medicine, University of Colorado Health Sciences Center at Fitzsimons, Aurora, CO, USA
BMC Microbiology 2011, 11:48 doi:10.1186/1471-2180-11-48Published: 4 March 2011
Hepatitis B virus (HBV) infections play an important role in the development of hepatocellular carcinoma (HCC). HBV X protein (HBx) is a multifunctional protein that can modulate various cellular processes and plays a crucial role in the pathogenesis of HCC. HBx is known to interact with DNA helicase components of TFIIH, a basal transcriptional factor and an integral component of DNA excision repair.
In this study, the functional relevance of this association was further investigated in the context to DNA repair. By site-directed mutagenesis HBx's critical residues for interaction with TFIIH were identified. Similarly, TFIIH mutants lacking ATPase domain and the conserved carboxyl-terminal domain failed to interact with HBx. Yeast and mammalian cells expressing HBxwt conferred hypersensitivity to UV irradiation, which is interpreted as a basic deficiency in nucleotide excision repair. HBxmut120 (Glu to Val) was defective in binding to TFIIH and failed to respond to UV.
We conclude that HBx may act as the promoting factor by inhibiting DNA repair causing DNA damage and accumulation of errors, thereby contributing to HCC development.