OBJECTIVETo verify if mutated polyadenylation signal retroviruses can produce viral-host readthrough transcripts (Rth) and have the ability to transform human gastric epithelial GES-1 cells, and to discuss the new functions of retroviruses in gastric cancer related gene research.

METHODSThe polyadenylation signal-deficient retrovirus vector mutated by PCR site-directed mutagenesis was used to make polyadenylation signal-deficient retroviruses by PA317 packaging cells. The GES-1 cells were infected by the viruses and selected by G418. Viral-host readthrough RNAs were checked by Northern blot. The cell growth and soft agar assay were run to test the transformed cells.

RESULTSpolyadenylation signal-deficient retroviruses could be packaged by PA317 packaging cells. The viruses had the ability to infect GES-1 cells. Northern blot analysis of viral RNA from infected pools and individual G418-resistant clones demonstrated that mutation of consensus LTR polyadenylation signals generated Rth viral RNA in the infected GES-1 cells. Phenotypic analysis results showed that the GES-1 cells infected with plyadenylation signal mutant viruses tended to grow in a cluster manner. Pools of PA317 cells infected with mutant viruses were able to form colonies in soft agar with a higher efficiency than control or uninfected cells.

CONCLUSIONHost readthrough transcripts generated by polyadenylation signal mutant viruses may contribute to transformation GES-1 cell phenotypes. The mutant vectors and the method described in the present work may be useful as tools to trap and identify genes involved in retroviral insertion mediated cell transformation.