Functional analysis of transactivation by mutants of hepatitis B virus X gene in human hepatocellular carcinoma.
The X protein of the hepatitis B virus transactivates various cellular and viral promoters and enhancers. In this study, wild-type and mutants of the X gene, including the point mutations at codons 130 (AAG-->ATG, lysin-->methionine) and 131 (GTC-->ATC, valine-->isoleucine), commonly found in patients with human hepatocellular carcinoma (HCC), or deletions encompassing the same region, were cloned and inserted into expression vectors. Functional analysis of the mutants of the X gene was performed on the long terminal repeat of the Rous sarcoma virus in a transient transfection assay. A transactivating function was observed in the vector containing point mutations at codons 130 and 131 at the same level as that of wild-type X gene. Two constructs, each containing a different type of 8-nucleotide deletion mutant (codons 128-130 or 130-132,) dramatically lost their transactivating function. These findings suggest that the transactivating function is not necessarily associated with the development of HCC, and that not only transactivation by the X gene but also the mutation-enhanced oncogenic potential of the gene products could contribute to hepatocarcinogenesis.
Minemura
Masami
M
Third Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan.
Shimizu
Yukihiro
Y
Hirano
Katsuharu
K
Nakayama
Yasuhiro
Y
Tokimitsu
Yoshiharu
Y
Tajiri
Kazuto
K
Yamada
Kazuki
K
Xue
Feng
F
Takahara
Terumi
T
Watanabe
Akiharu
A
Sugiyama
Toshiro
T
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D002474:Cell-Free System; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D014176:Protein Biosynthesis / Q000235:genetics; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins
D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein