title: Proteomic profiling identifies aberrant epigenetic modifications induced by hepatitis B virus X protein.
abstract: The hepatitis B virus-encoded X (HBx) protein coactivates transcription of a variety of viral and cellular genes and it is believed to play essential roles in viral replication and hepatocarcinogenesis. To examine the pleiotropic effects of HBx protein on host cell protein expression, we utilized 2-DE and MS analysis to compare and identify differentially expressed proteins between a stable HBx-transfected cell line (HepG2-HBx), constitutively expressing HBx, and vector control cells. Of the 60 spots identified as differentially expressed (+/- over 2-fold, p < 0.05) between the two cell lines, 54 spots were positively identified by MS/MS analysis. Several recent studies suggested that HBx was involved in regional hypermethylation of tumor suppressor genes and global hypomethylation of satellite 2 repeats during hepatocarcinogenesis; however, no specific gene has been reported as hypomethylated by HBx. Promoter methylation analysis was examined for those protein spots showing significant alterations, and our results revealed that specific genes, such as aldehyde dehydrogenase 1 (ALDH1), can be hypomethylated by HBx, and two calcium ion-binding proteins, S100A6 and S100A4, were hypermethylated by HBx and could be re-expressed by AZA (DNA methylase inhibitor) treatment. Moreover, via cluster and pathway analysis, we proposed a hypothetical model for the HBx regulatory circuit involving aberrant methylation of retinol metabolism-related genes and calcium homeostasis-related genes. In summary, we profiled proteome alterations between HepG2-HBx and control cells, and found that HBx not only induces regional hypermethylation but also specific hypomethylation of host cell genes.
authors.affiliation: West China Hospital, Sichuan University, Chengdu, 610041, People's Republic of China.
authors.forename: Aiping
authors.initials: A
authors.lastname: Tong
authors.forename: Lantu
authors.initials: L
authors.lastname: Gou
authors.forename: Quek Choon
authors.initials: QC
authors.lastname: Lau
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Xia
authors.initials: X
authors.lastname: Zhao
authors.forename: Jiong
authors.initials: J
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Tang
authors.forename: Lijuan
authors.initials: L
authors.lastname: Chen
authors.forename: Minghai
authors.initials: M
authors.lastname: Tang
authors.forename: Canhua
authors.initials: C
authors.lastname: Huang
authors.forename: Yu-quan
authors.initials: YQ
authors.lastname: Wei
mesh_terms: D002460:Cell Line; D019175:DNA Methylation; D015180:Electrophoresis, Gel, Two-Dimensional; D044127:Epigenesis, Genetic; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D040081:Protein Array Analysis; D020543:Proteome / Q000032:analysis*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D020543:Proteome; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein