Sequence from early region of polyoma virus DNA containing viral replication origin and encoding small, middle and (part of) large T antigens

Mechanisms for the incorporation of proteins in membranes and organelles.

“…Processing of this RNA would eliminate the secretory segment, which is now treated as part of an intronic region, to yield the tLm mRNA. This phenomenon, in which different forms of messenger RNA for related proteins are derived from a single "gene," is somewhat analogous to what occurs in polyoma virus-transformed cells : three different forms of tumor antigen, with identical amino-terminal sequences (92, 210) but substantially different carboxy-terminal regions and different subcellular localizations (nuclear, plasma membrane, and cytoplasmic) (97), apparently originate from a single RNA precursor (215,62). In this case, nature seems to have already performed an experiment that demonstrates that the specific subcellular localization of each of these polypeptides, which most likely are synthesized in free polysomes, cannot be determined by the amino-terminal sequences that are common to all of them.…”

Xrep, a plasmid-stimulating X chromosomal sequence bearing similarities to the BK virus replication origin and viral enhancers

“…Within the ELS sequence of Xrepa, a 19 base pair true palindrome was found which is quite similar to true palindromes located near the replication origins of SV40, BK and polyoma viruses (4). These are the region I sequences described in the Introduction.…”

“…Soeda et al compared three DNA viruses, BK, SV40 and polyoma, and found that all three had similar "true" palindromes of the general configuration: CCTC(N)nCTCC at their replication origins (4). Another study in which this same sequence is referred to as an "inverted repeat" showed that deletion of this region results in a drastic reduction in the replicative activity of SV40 (5).…”

“…The pentanucleotide contacts that T antigen makes in its binding region I are the most conserved feature of the true palindromes comparing SV40, BK and polyoma (4,6). There is evidence that region I may have a bent DNA conformation (10).…”

Cloning of a defective polyoma DNA molecule with rearrangements in the region coding for middle and large T antigens

“…Its transforming activity has been linked to the early region of the viral genome. This region, which is expressed early after infection and in transformed cells, codes for three proteins: the large (100 K), middle (55 K), and small (22 K) T antigens [2]. Although the transformed state of some rat cells has been reported to require the entire early region [3], several lines of evidence suggest that large T antigen is not essential for transformation.…”