Functional analysis of hepatitis B virus pre-s deletion variants associated with hepatocellular carcinoma.
BACKGROUND
Naturally occurring pre-S deletion mutants have been identified in hepatitis B carriers and shown to be associated with the development of hepatocellular carcinoma. The phenotypes of these pre-S deletion genomes remain unclear, and they were investigated in this study.


METHODS
The pre-S deletion genomes: (1) pre-S1 deletion, (2) deletion spanning pre-S1 and pre-S2, (3) pre-S2 N-terminal deletion, and (4) pre-S2 internal deletion were constructed and analyzed by transfection into Huh-7 cells.


RESULTS
Functional analyses reveal that these mutants were divided into two groups: S promoter deletion and non-S promoter deletion variants. Compared with the wild-type genome, S promoter deletion variants led to an inverse ratio of pre-S1 mRNA and pre-S2/S mRNA, and intracellular accumulation of surface proteins. An interesting finding is that a small amount of L proteins was detected in the medium from S promoter deletion variant-transfected cells. Non-S promoter deletion variants conversely displayed a wild-type like mRNA and protein pattern. The secretion of surface proteins from non-S promoter deletion variants was inhibited less than from S promoter deletion variant. Immunofluorescence analysis showed mutant surface proteins colocalized with ER and exhibited an atypical distribution: granular staining pattern in the S-promoter deletion variants and perinuclear staining pattern in the non-S promoter deletion variants.


CONCLUSIONS
This study shows that these pre-S deletion genomes exhibit two different phenotypes in mRNA transcription, surface protein expression and secretion. This diversity seems to result from the deletion of S promoter rather than result from the deletion of pre-S1 or pre-S2.
School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan.
Chih-Ming
CM
Lin
Gen-Ming
GM
Wang
Guey-Mei
GM
Jow
Bing-Fang
BF
Chen
D006528:Carcinoma, Hepatocellular / Q000821:virology*; D045744:Cell Line, Tumor; D015967:Gene Expression Regulation, Viral; D006509:Hepatitis B / Q000821:virology; D006514:Hepatitis B Surface Antigens / Q000235:genetics*; D006513:Hepatitis B e Antigens / Q000235:genetics / Q000378:metabolism; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008113:Liver Neoplasms / Q000821:virology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011498:Protein Precursors / Q000235:genetics*; D017384:Sequence Deletion; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism
D006514:Hepatitis B Surface Antigens; D006513:Hepatitis B e Antigens; D008565:Membrane Proteins; D011498:Protein Precursors; D014758:Viral Core Proteins; C050806:presurface protein 1, hepatitis B surface antigen; C050807:presurface protein 2, hepatitis B surface antigen