SAGE transcript profiles of normal primary human hepatocytes expressing oncogenic hepatitis B virus X protein

Abstract

Hepatitis B virus (HBV) is a major risk factor for hepatocellular carcinoma (HCC). HBV encodes an oncogenic HBx gene that functions as a transcriptional coactivator of multiple cellular genes. To understand the role(s) of HBx in the early genesis of HCC, we systematically analyzed gene expression profiles by serial analysis of gene expression (SAGE) in freshly isolated human primary hepatocytes infected with a replication-defective adenovirus containing HBx. A total of 19,501 sequence tags (representing 1443 unique transcripts) were analyzed, which provide a distribution of a transcriptome characteristic of normal hepatocytes and a profile associated with HBx expression. Examples of the targeted genes were confirmed by the Megarray analysis with a significant correlation between quantitative SAGE and Megarray (r = 0.8, P < 0.005). In HBx-expressing hepatocytes, a total of 57 transcripts (3.9%) were induced, and 46 transcripts (3.3%) were repressed by more than fivefold. Interestingly, most of the HBx-up-regulated transcripts can be clustered into three major classes, including genes that encode ribosomal proteins, transcription factors with zinc-finger motifs, and proteins associated with protein degradation pathways. These results suggest that HBx may function as a major regulator in common cellular pathways that, in turn, regulate protein synthesis, gene transcription, and protein degradation.

Gene expression profiling of human HBV- and/or HCV-associated hepatocellular carcinoma cells using expressed sequence tags

“…Comparative analysis of HBV-and HCV-associated HCC cell lines revealed that many ribosomal-related genes such as RPL family genes were up-regulated in HBV-associated HCC cell lines (HBVHCCs) in comparison to HCV-associated HCC cell lines (HCV-HCCs), suggesting the activation of protein translation in HBV-HCCs. This observation is consistent with the previous report that major classes of genes encoding ribosomal proteins were up-regulated by the HBX protein (19). In addition, genes involved in extracellular matrix and cytoskeletal organization, such as ANXA2, KRT8, CKAP4, KRT7 and CFL1, were shown to be up-regulated in HBV-HCCs, as well as genes such as K-ALPHA-1, ANXA1, ACTB, and ANXA5 in HCV-HCCs.…”

“…The application of global approaches such as the collection of expressed sequence tags (ESTs), Serial Analysis of Gene Expression (SAGE) and microarray techniques have been shown to be useful in the analysis of complex biological phenomena, including human diseases (15,(17)(18)(19)(20)(21). Among these approaches, the expressed sequence tags (ESTs) generated by the single-pass sequencing of randomly selected cDNA clones from cDNA libraries have been used to identify novel genes (22).…”

Altered Proteolysis and Global Gene Expression in Hepatitis B Virus X Transgenic Mouse Liver

“…In SAGE-based analysis of the transcriptional profiles on normal primary human hepatocytes expressing HBX protein by transient transfection, Wu et al observed that the up-regulated genes fell into three categories, including genes encoding ribosomal protein, transcription factors with the zinc finger motif, multiple proteasome subunits, ubiquitin, and ubiquitinassociated proteins (33). Some of these changes showed a pattern similar to that found in our transgenic mouse model expressing the HBX protein, although the genes with significant changes are different.…”

Activating mechanism of transcriptor NF-kappaB regulated by hepatitis B virus X protein in hepatocellular carcinoma

“…The results of nuclear location of ubiquitin and its relativity with IκB-α indicated the proteolysis of IκB-α was processed in tumor cell nuclei. Of course, another likelihood was that transcription of ubiquitin would be promoted after NF-κB activation [27] . There is no relativity between ubiquitin and HBx, so whether the proteolysis of HBx passes through non-ubiquitin pathway or not remains to be determined.…”