Bovine papilloma virus contains an activator of gene expression at the distal end of the early transcription unit.

Abstract

Bovine papilloma virus (BPV) contains a cis-acting DNA element which can enhance transcription of distal promotors. Utilizing both direct and indirect transient transfection assays, we showed that a 59-base-pair DNA sequence from the BPV genome could activate the simian virus 40 promoter from distances exceeding 2.5 kilobases and in an orientation-independent manner. In contrast to the promoter 5'-proximal localization of other known viral activators, this element was located immediately 3' to the early polyadenylation signal in the BPV genome. Deletion of these sequences from the BPV genome inactivated the transforming ability of BPV recombinant plasmids. Orientation-independent reinsertion of this 59-base-pair sequence, or alternatively of activator DNA sequences from simian virus 40 or polyoma virus, restored the transforming activity of the BPV recombinant plasmids. Furthermore, the stable transformation frequency of the herpes simplex virus type 1 thymidine kinase gene was enhanced when linked to restriction fragments of BPV DNA which included the defined activator element. This enhancement was orientation independent with respect to the thymidine kinase promoter. The enhancement also appeared to be unrelated to the establishment of the recombinant plasmids as episomes, since in transformed cells these sequences are found linked to high-molecular-weight DNA Bovine papilloma virus type 1 (BPV) provides a model system in mammalian cells for testing the assumptions implicit in the arguments described above. BPV viral DNA, as well as a 69% subgenomic fragment (69T), can transform rodent cells in culture (26); the viral genome in these cells is maintained as a multicopy nuclear episome (2a, 24). We reasoned that linking a selectable genetic marker to the BPV genome might substantially increase the transformation efficiency of that marker, by bypassing the need for integration of the foreign DNA. In this way we could test whether the establishment of the transforming DNA is a limiting step in transformation.We have reported previously (27) that linking BPV DNA to the herpes simplex virus (HSV) thymidine kinase (TK) gene can enhance the transformation frequency of TK-cells to TK+ more than 100-fold. This effect is independent of the position and orientation of the BPV sequences relative to the direction of HSV TK transcription. However, the enhanced transfor-1108 on May 7, 2018 by guest

Structure, DNasel hypersensitivity and expression of integrated papilloma virus in the genome of HeLa cells

“…Two pairs of them, EL-l/EL-3 and EL-4/ EL-5, appear forming a direct repeat with 20 and 18 nucleotides respectively as spacer, which is an organization similar to that of the 'enhancer' in other papova viruses as reported by Lusky et al [34]. The location and orientation of enhancer-like sequences are indicated in Fig.…”

Multiple sequence motifs are involved in SV40 enhancer function.

“…[bovine papillomavirus (Lusky et al, 1983;Weiher and Botchan, 1984), adenovirus ElA (Hen et al, 1983), immunoglobulin xlight chain (Queen and Stafford, 1984) Figure 3B and pA213 in Figure 2A) does not abolish domain B activity. Furthermore, deleting GT-motif II can be compensated for by juxtaposing domain C to GT-motif I (compare pA104 with pA54 in Figure 2A).…”

A very strong enhancer is located upstream of an immediate early gene of human cytomegalovirus

“…In spite of some encouraging results Lusky et al, 1983;Hearing and Shenk, 1983;Nordheim and Rich, 1983;Hen et al, 1983), it seems difficult to detect a sequence motif common to all enhancers. Rather, scattered short homologies are shared by subgroups of enhancers, and it appears that several types of sequence motifs can be assorted in many combinations to make up an enhancer .…”

“…Heterologous enhancers have been shown to substitute for the enhancer of SV40 or polyoma virus, allowing T antigen expression and viral DNA replication (de Villiers et al, 1982;Levinson et al,, 1982;Lusky et al, 1983;Fried et al, 1983). This has allowed us to develop a method for detection of enhancer elements in large genomes by an "enhancer trap" assay.…”