Publisher Summary From a variety of data associated with earlier studies, it was concluded that there was no obvious correlation between polyomavirus induced transformation and cellular chromosomal changes Much now is known about the structural organization of the virus, and many predictions about gene expression and expected cellular responses to viral products can be made Several of the proteins, notably middle and large T-antigens, as well as the viral capsid species VP 1, appear to consist of closely related “families” of proteins, rather than unique and discrete molecules The possibility must be faced that individual members of a particular family might have different functions One of the more interesting of the relationships among the viral proteins is that between the middle and small T-antigens Deoxyribonucleic acid (DNA) sequence analysis predicts that with the exception of the C-terminal tetrapeptide, all of the amino acids found in small T-antigen are also present in middle T-antigen Early optimism regarding the use of viruses to understand many important cellular events has not been misplaced As more “control” signals, such as those leading to DNA replication, become defined in lower organisms in terms of structural elements within the genome and similar elements are identified in viruses such as polyoma, it would be surprising if they did not prove faithful mimes of the corresponding events in mammalian cells Thus, the concept of polyomavirus as an excellent tool for understanding its host should gain further support within the next few years

Polyomavirus: an overview of its unique properties.

By using a DNA fragment immunoassay, the binding of simian virus 40 (SV40) and polyomavirus (Py) large tumor (T) antigens to regulatory regions at both viral origins of replication was examined. Although both Py T antigen and SV40 T antigen bind to multiple discrete regions on their proper origins and the reciprocal origin, several striking differences were observed. Py T antigen bound efficiently to three regions on Py DNA centered around an MboII site at nucleotide 45 (region A), a BglI site at nucleotide 92 (region B), and another MboII site at nucleotide 132 (region C). Region A is adjacent to the viral replication origin, and region C coincides with the major early mRNA cap site. Weak binding by Py T antigen to the origin palindrome centered at nucleotide 3 also was observed. SV40 T antigen binds strongly to Py regions A and B but only weakly to region C. This weak binding on region C was surprising because this region contains four tandem repeats of GPuGGC, the canonical pentanucleotide sequence thought to be involved in specific binding by T antigens. On SV40 DNA, SV40 T antigen displayed its characteristic hierarchy of affinities, binding most efficiently to site 1 and less efficiently to site 2. Binding to site 3 was undetectable under these conditions. In contrast, Py T antigen, despite an overall relative reduction of affinity for SV40 DNA, binds equally to fragments containing each of the three SV40 binding sites. Py T antigen, but not SV40 T antigen, also bound specifically to a region of human Alu DNA which bears a remarkable homology to SV40 site 1. However, both tumor antigens fail to precipitate DNA from the same region which has two direct repeats of GAGGC. These results indicate that despite similarities in protein structure and DNA sequence, requirements of the two T antigens for pentanucleotide configuration and neighboring sequence environment are different.

Simian virus 40 and polyomavirus large tumor antigens have different requirements for high-affinity sequence-specific DNA binding.

As a new gardening year begins, the question of what seeds do we need and where do we get them arises. For common varieties, the most convenient and economical sources are local farm supply stores and seed racks in local stores. For less common seeds we turn to mail order and/or the internet. Most mail order firms have web sites where catalogs can be requested. A sampling of catalogs and their web sites follows:

The garden path

The group of small, double-stranded DNA tumour viruses, classified as papova viruses, have received considerable attention following the discovery of the first member of this species, papilloma virus, in 1933 by Shope in rabbits. Since Shope’s discovery, papilloma viruses have been recovered from the warts of many other animals, including humans (for review, see reference 1). The other members of the species which have provided the name for this class of viruses, polyoma, a mouse virus, and the vacuolating virus of rhesus monkeys, SV40, were not isolated until 1953 and 1960, respectively (for review, see references 2–4). Since then a number of human papova viruses have been discovered (for review, see reference 5) and most recently, a papovavirus of hamsters (6) was isolated. Thus this class of viruses, all capable of producing cellular transformation in appropriate tissue culture systems, or tumours in suitable animal models, is ubiquitous throughout the animal kingdom. The association with malignancies has provided the stimulus for many different studies. The very small sizes of the viruses (between about 5,000 and 10,000 base pairs) offers the possibility that the virus-host cell interactions that ultimately result in production of a cancer-like cell can eventually be elucidated.

Frank McCormick

Papers

Immunological cross-reaction between large T-Antigens of SV40 and polyoma vir