Mouse cells transformed by bovine papillomavirus contain only extrachromosomal viral DNA sequences.

Abstract

The viral DNA sequences in mouse C127 cells transformed by bovine papillomavirus type 1 (BPV-1) virions, by full-length linear BPV-1 DNA, or by a defined transforming subgenomic DNA segment of BPV-1 were examined by reassociation kinetics and blot hybridization. In all cases, the transformed cells contained multiple copies ofBPV-1 DNA, present exclusively as supercoiled or nicked circular extrachromosomal molecules or as a slowly migrating complex of circular viral DNA molecules. In the transformed cell lines established from cells transfected with full-length linear BPV-1 DNA, there was recircularization of the input DNA which in some cases resulted in the loss of the restriction site used in the linearization of the DNA. In the transformed cell lines established with the defined subgenomic segment there was circularization of the DNA accompanied by the acquisition of new sequences or duplication and rearrangement of the BPV-1 sequences. In contrast to other well-studied virus transformation systems, no integration of the BPV-1 genome into the host chromosome could be detected under conditions sensitive enough to detect 0.14.2 viral genome equivalent. It was concluded that maintenance oftransformation may be mediated by nonintegrated viral DNA.Cellular transformation induced by several DNA and RNA viruses has been studied in considerable detail. In most of these systems, cellular transformation is accompanied by integration of the viral sequences required for the maintenance of transformation. Plasmid viral DNA forms have been described in cells transformed by certain DNA viruses, but almost always in association with integrated viral DNA. The papillomaviruses represent a tumor virus system which for technical reasons has received relatively little attention. The papillomaviruses along with the polyomaviruses comprise the papovavirus family (Papovaviridae) (1). Despite the morphologic similarities of their virion and genomic structures, the papillomaviruses and the polyomaviruses are separate groups ofviruses, distinguished by biological, serological, and biochemical features (2-4).The papillomaviruses are widely distributed in nature and induce benign skin tumors (warts) in their natural hosts which include humans, cattle, rabbits, dogs, sheep, chaffinches, and horses. Most papillomaviruses are highly host specific, and this property, together with the lack of an adequate tissue culture system for their propagation, has hampered studies of their molecular biology and genetics. Recently, this liability has been partially circumvented by molecularly cloning the genomes of a number of different papillomaviruses in Escherichia coli by using the certified plasmid pBR322 as cloning vector (5, 6).Whereas the proliferative changes induced by most papillomaviruses are limited to epidermal cells, lesions induced by the bovine fibropapillomaviruses (BPV-1 and BPV-2) are exceptional in that they consist of both epidermal and mesenchymal proliferative components (7). These BPVs also differ in that they can induce ...

Transformation of Human Embryonic Fibroblasts by BK Virus, BK Virus DNA and a Subgenomic BK Virus DNA Fragment

“…5, lane 12): in addition to the four HindlII fragments, two bands were observed which may derive from virus integrations and/or from defective polymeric BKV D N A molecules lacking one or more HindlII restriction sites. The single-strand specific nuclease S1 converts circular monomeric and catenated polymeric forms of papovavirus D N A to monomeric linear molecules (Germond et al, 1974;Beard et ai., 1973;Chowdhury et al, 1975;Law et al, 1981). We found that BKV D N A F I and FII were converted to full-length linear molecules by digestion with nuclease S1 (data not shown).…”

Integrated Shope Virus DNA is Present and Transcribed in the Transplantable Rabbit Tumour Vx-7

“…Physical state of virus DNA in the Vx-7 cell Recent studies of bovine and rabbit papilloma virus DNAs (see Law et al, 1981;F. O. Wettstein & J. G. Stevens, unpublished results) have shown that the virus genomes generally exist in a non-integrated state.…”

The Physical State of Hybrid Genomes Containing Simian Virus 40 and Bovine Papilloma Virus DNA Sequences in Transformed Clonal Cell Lines

“…Both tissue culture cells transformed by bovine papillomavirus type 1 (BPV-1) and cells in solid tumours that were induced by BPV-1 contain only non-integrated viral genomes (Amtmann et al, 1980;Lancaster, 1981 ;Law et al, 1981 ;Moar et al, 1981 ;Pfister et al, 1981). In contrast, the DNA of simian virus 40 (SV40) consistently integrates randomly into the DNA of the transformed cells (Sambrook et al, 1968), but no specific cell or viral integration sites have been detected (Botchan et al, 1976;Ketner & Kelly, 1976).…”