cis-active elements from mouse chromosomal DNA suppress simian virus 40 DNA replication

Abstract

Simian virus 40 (SV40)-containing DNA was rescued after the fusion of SV40-transformed VLM cells with permissive COS1 monkey cells and cloned, and prototype plasmid clones were characterized. A 2-kilobase mouse DNA fragment fused with the rescued SV40 DNA, and derived from mouse DNA flanking the single insert of SV40 DNA in VLM cells, was sequenced. Insertion of the intact rescued mouse sequence, or two nonoverlapping fragments of it, into wild-type SV40 plasmid DNA suppressed replication of the plasmid in TC7 monkey cells, although the plasmids expressed replication-competent T antigen. Rat cells were transformed with linearized wild-type SV40 plasmid DNA with or without fragments of the mouse DNA in cis. Although all of the rat cell lines expressed approximately equal amounts of T antigen and p53, transformants carrying SV40 DNA linked to either of the same two replication suppressor fragments produced significantly less free SV40 DNA after fusion with permissive cells than those transformed by SV40 DNA without a cellular insert or with a cellular insert lacking suppressor activity. The results suggest that two independent segments of cellular DNA act in cis to suppress SV40 replication in vivo, either as a plasmid or integrated in chromosomal DNA.

Two cellular single-strand-specific DNA-binding proteins interact with two regions of the bovine papillomavirus type 1 genome, including the origin of DNA replication

“…of the simian virus 40 (SV40) origin of replication, a fragment containing the autonomous replication sequence (ARS) consensus sequence of S. cerevisiae, the lexA and actin gene promoters of S. cerevisiae, a mouse cellular DNA fragment interfering with SV40 DNA replication (8), and many more enhancer and promoter sequences. As an example, oligonucleotides PyE-l and BE-l from the polyomavirus enhancer B and the distal BPV-1 enhancer are included in all panels of Fig.…”

Papillomavirus contains cis-acting sequences that can suppress but not regulate origins of DNA replication

“…Both the slower replication rate of IM plasmids relative to that of Pyori and the slower rate of reinitiation within a single S phase, reflecting a slower overall rate of IM replication relative to that of Pyori, suggest that suppression by NCOR sequences reduces the frequency at which origins can initiate replication. The same might be said of other "poison" sequences that suppress the activity of papovavirus origins (20,27). Although this mechanism of suppression represents an artifact of experimental conditions (T-ag is normally not present during BPV DNA replication), it is possible that papillomavirus gene products other than El and E2 may substitute for T-ag and utilize NCOR sequences to maintain a low BPV copy number in transformed cells by suppressing the frequency of initiation at BPV on.…”