title: Transactivation of proto-oncogene c-Myc by hepatitis B virus transactivator MHBst167.
abstract: C-terminally truncated hepatitis B virus (HBV) middle size surface proteins (MHBst) has been shown to be a transcriptional activator and may be relevant to hepatocarcinogenesis by transactivating gene expression. In the present study, a pcDNA3.1(-)-MHBst167vector coding for MHBsttruncated at amino acid 167 (MHBst167) was constructed and transfected into the HepG2 hepatoma cell line. mRNA and protein expression of MHBst167in the cells was detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis. A cDNA library of genes transactivated by the truncated protein in HepG2 cells was made in pGEM-T Easy using suppression subtractive hybridization. The cDNAs were sequenced and analyzed with BLAST searching against the sequences in GenBank. The results showed that certain sequences, such as that of human proto-oncogene c-Myc, may be involved in tumor development. An expression vector pCAT3/c-Myc containing the chloramphenicol acetyltransferase (CAT) gene under the control of a c-Myc promoter was generated, and the transcriptional transactivating effect of MHBst167on the c-Myc promoter was investigated by RT-PCR and western blotting. MHBst167was found to upregulate the transcriptional activity of the promoter, as well as transcription and translation of c-Myc. MHBst167was also shown to transactivate SV40 immediate early promoter, and transcriptionally transactivate the expression of human c-Myc. These findings provide new directions for studying the biological functions of MHBst167, and for a better understanding of the tumor development mechanisms of HBV infection.
authors.affiliation: Liaoning Provincial University Key Laboratory of Biophysics, College of Medicine, Dalian University, Dalian, Liaoning 116622, P.R. China.
authors.forename: Yong-Zhi
authors.initials: YZ
authors.lastname: Lun
authors.affiliation: Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, P.R. China.
authors.forename: Jun
authors.initials: J
authors.lastname: Cheng
authors.affiliation: Liaoning Provincial University Key Laboratory of Biophysics, College of Medicine, Dalian University, Dalian, Liaoning 116622, P.R. China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Chi
authors.affiliation: Liaoning Provincial University Key Laboratory of Biophysics, College of Medicine, Dalian University, Dalian, Liaoning 116622, P.R. China.
authors.forename: Xue-Lei
authors.initials: XL
authors.lastname: Wang
authors.affiliation: Liaoning Provincial University Key Laboratory of Biophysics, College of Medicine, Dalian University, Dalian, Liaoning 116622, P.R. China.
authors.forename: Meng
authors.initials: M
authors.lastname: Gao
authors.affiliation: Liaoning Provincial University Key Laboratory of Biophysics, College of Medicine, Dalian University, Dalian, Liaoning 116622, P.R. China.
authors.forename: Li-DA
authors.initials: LD
authors.lastname: Sun
keywords: MHBst167; SV40 early promoter; proto-oncogene c-Myc; suppression subtractive hybridization; transactivation