Molecularly Cloned Bovine Papillomavirus DNA Transforms Mouse Fibroblasts in Vitro

Abstract

SUMMARYNIH 3T3 mouse fibroblasts were transformed in vitro by transfection with viral DNA from bovine papillomavirus (BPV) types 4, 2 and 1. The viral DNAs were molecularly cloned in pAT153 to construct pBV4, a recombinant plasmid containing the whole genome of BPV4, pBV2 containing the entire genome of BPV2, and pBV1-D1 which contains the 69~ transforming DNA fragments of BPV1. The transformed cells lost contact inhibition, were anchorage-independent, required low serum and were tumourigenic in nude mice. This is the first report of cell transformation in vitro by BPV4 DNA. The recombinant plasmids transformed NIH 3T3 cells with an efficiency of 200 to 300 foci/~tg DNA. Cleavage of the recombinant plasmids with enzymes that separate the viral DNA from pAT153 DNA did not significantly alter the efficiency of transformation. In all the transformed cells analysed, the recombinant plasmids were found as multiple copies of non-integrated monomers.

The bovine papillomavirus genome and its uses as a eukaryotic vector

“…This decrease in efficiency was the same whether the complete pBR322 plasmid or a 'poison minus' derivative, pML, was used (in contrast to analogous experiments with SV40 [55]). An interesting observation in this context was reported by Campo et al [56]. They linked plasmid pAT153, a derivative of pBR322 containing a deletion which is not as extensive as pML [57], to the 69 % transforming region and achieved normal levels of transformation.…”

“…If however the whole BPV genome is used different results are obtained. Thus when bacterial sequences such as pML or pAT153 are linked to the whole BPV genome normal transformation efficiencies are obtained, but linkage of the complete pBR322 moiety resulted in a 200-fold decrease in transformation efficiency [43,56,59]. These results exemplify three basic types of BPV plasmid vectors, the essential characteristics of which are illustrated in Fig.…”

Viral DNA Sequences Detected in a Hamster Liposarcoma Induced by Bovine Papillomavirus Type 4

“…BPV type 4 (BPV-4) is particularly interesting since BPV-4-induced papillomas are found in cattle with squamous carcinoma of the alimentary tract which is associated with the eating of bracken fern (Pteridium aquilinum) (Campo et al, 1980;Jarrett et al, 1978a, b). The BPV-4 genome is oncogenic since it transforms NIH 3T3 cells in culture and the resulting BPV-4 DNA-containing cell lines are tumourigenic in nude mice (Campo & Spandidos, 1983). So far, however, there are no reports of BPV-4 being directly carcinogenic in the natural or a heterologous host.…”

“…The BPV-4 genome is oncogenic since it transforms NIH 3T3 cells in culture and the resulting BPV-4 DNA-containing cell lines are tumourigenic in nude mice (Campo & Spandidos, 1983). So far, however, there are no reports of BPV-4 being directly carcinogenic in the natural or a heterologous host.…”

“…However, what makes the present report particularly interesting is the demonstration that it is BPV-4 which can exert a direct carcinogenic potential in a heterologous host. So far, there has only been an indication that this might be so, since cloned BPV-4 DNA transfects and transforms mouse NIH 3T3 cells in culture, the resulting cell lines being tumourigenic in nude mice (Campo & Spandidos, 1983). Previously reported inductions of tumours by BPV in heterologous hosts have almost certainly not been due to BPV-4 since this virus is exclusively found in alimentary tract papillomas (Campo et al, 1980Jarrett, 1985) and alimentary tract papillomas were never used for isolation of virus (Olson & Cook, 1951 ;Gordon & Olson, 1968;Robl & Olson, 1968;Moar et al, 1981).…”