A trans-activator function is generated by integration of hepatitis B virus preS/S sequences in human hepatocellular carcinoma DNA.
The X gene of wild-type hepatitis B virus or integrated DNA has recently been shown to stimulate transcription of a variety of enhancers and promoters. To further delineate the viral sequences responsible for trans-activation in hepatomas, we cloned the single hepatitis B virus insert from human hepatocellular carcinoma DNA M1. The plasmid pM1 contains 2004 base pairs of hepatitis B virus DNA subtype adr, including truncated preS/S sequences and the enhancer element. The X promoter and 422 nucleotides of the X coding region are present. The entire preC/C gene is deleted. In transient cotransfection assays using Chang liver cells (CCL 13), pM1 DNA exerts a 6- to 10-fold trans-activating effect on the expression of the pSV2CAT reporter plasmid. The trans-activation occurs by stimulation of transcription and is dependent on the simian virus 40 enhancer in the reporter plasmid. Deletion analysis of pM1 subclones reveals that the trans-activator is encoded by preS/S and not by X sequences. A frameshift mutation within the preS2 open reading frame shows that this portion is indispensable for the trans-activating function. Initiation of transcription has been mapped to the S1 promoter. A comparable trans-activating effect is also observed with cloned wild-type hepatitis B virus sequences similarly truncated. These results show that a transcriptional trans-activator function not present in the intact gene is generated by 3' truncation of integrated hepatitis B virus DNA preS/S sequences.
Caselmann
W H
WH
Max-Planck-Institut für Biochemie, Department of Virus Research, Martinsried, Federal Republic of Germany.
Meyer
M
M
Kekulé
A S
AS
Lauer
U
U
Hofschneider
P H
PH
Koshy
R
R
D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000382:microbiology*; D002460:Cell Line; D002872:Chromosome Deletion; D004273:DNA, Neoplasm / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics* / Q000302:isolation & purification; D015698:Genomic Library; D006515:Hepatitis B virus / Q000235:genetics* / Q000502:physiology; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000382:microbiology*; D008242:Lysogeny; D008297:Male; D008875:Middle Aged; D010957:Plasmids; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D004273:DNA, Neoplasm; D004279:DNA, Viral; D015534:Trans-Activators