EXPRESSION OF THE NONSTRUCTURAL PROTEINS OF PARVOVIRUS MVMP FROM RECOMBINANT RETROVIRUSES - PREDOMINANT ROLE OF THE PARVOVIRAL NS-1 PRODUCTIN HOST-CELL DISTURBANCE

Stable Psi-2 cell transformants were selected for their resistance to neomycin after transfection with a retroviral pZipNeo-SVX vector carry ing sequences encoding for the non-structural proteins of parvovirus m inute virus of mice (prototype strain, MVMp). Cells producing both NS- 1 and NS-2 proteins (PsiNS) or only the NS-2 polypeptide (PsiNS2) were obtained. PsiNS cells exhibited morphological abnormalities and had a reduced clone-forming ability, whereas PsiNS2 cells were indistinguis hable from the parental line. These cellular systems produced recombin ant retroviral particles which transduced the NS gene(s) into mouse A9 cells. As in the case of Psi-2 cells, A9 transformants expressing bot h NS-1 and NS-2 proteins were impaired in their cloning efficiency. Th ese results provided a direct confirmation of the predominant role of protein NS-1 in the cytopathic effect of parvoviruses.