Early Simian Virus Research Articles

Mapping of simian virus 40 early functions on the viral chromosome.

The simian virus 40 (SV40) DNA segment in the nondefective adenovirus 2-SV40 hybrid, Ad2(+)ND(4), is colinear with the segment between 0.11 and 0.59 SV40 fractional length from the site at which the R(1) restriction endonuclease cleaves SV40 DNA. This specifies the region of the SV40 DNA molecule which induces the early SV40 antigens: U antigen, tumor specific transplantation antigen, and T antigen. A variant of Ad2(+)ND(4), called Ad2(+)ND(4del), was found which has a deletion of the DNA segment between 0.50 and 0.57 SV40 fractional length from the R(1) endonuclease cleavage point.

"Early" virus-specific RNA may contain information necessary for chromosome replication and mitosis induced by Simian Virus 40.

Simian Virus 40 (SV40) induces in "contact-inhibited" tissue culture cells of mouse kidney an abortive infection that leads to the appearance of intra-nuclear SV40-specific tumor (T-) antigen, followed by replication of the mouse-cell chromatin and mitosis, while no viral progeny DNA or capsid protein is produced. Synthesis of "early" SV40-specific RNA ("19S RNA") begins a few hours before the appearance of T-antigen and appears to be switched off after the onset of chromatin replication. As the most simple working hypothesis that can account for the experimental results available, we assume that early SV40 RNA contains information necessary for production of T-antigen and that this antigen (or an unknown early virus-specific function that would simply parallel the appearance of T-antigen) activates or de-inhibits a cellular regulatory element that governs chromosome replication and mitosis. The experimental results agree with the idea that SV40 acts primarily as a mitogen.

Evidence for a transcription-control region of Simian virus 40 in the adenovirus 2--Simian virus 40 hybrid, Ad2+ND 1 .

The complementary DNA strands of the nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2(+)ND(1), were separated by isopycnic banding in a CsCl density gradient in the presence of synthetic polyribonucleotides. Separated strands were used in DNA-RNA hybridization reactions with RNA from cells productively infected by Ad2 or SV40, and with complementary SV40 RNA transcribed asymmetrically in vitro. About five times as much Ad2 RNA hybridized to the light stand of Ad2(+)ND(1) as to the heavy strand. Complementary RNA and early SV40 RNA (RNA synthesized before viral DNA replication) had significant homology only with the light strand. Only half as much of a preparation of RNA synthesized before and after viral DNA replication (early-plus-late SV40 RNA) hybridized to the light strand as to the heavy strand. These results indicate that templates for both late and early SV40 RNA are present in Ad2(+)ND(1). Therefore, the small SV40 segment within this virus (10-18% of the SV40 genome) must contain a transcription-control region. Ad2(+)ND(1) should thus be useful in the selective study of transcription as it occurs in cells infected by the oncogenic virus SV40.

Studies on nondefective adenovirus-simian virus 40 hybrid viruses. I. A newly characterized simian virus 40 antigen induced by the Ad2+ND 1 virus.

The nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2(+)ND(1), does not induce heat-labile SV40 T antigen but does induce a previously uncharacterized heat-stable SV40 antigen-the SV40 "U" antigen. This antigen is detectable by both immunofluorescence and complement fixation by using sera from hamsters with SV40 tumors. Sera from hamsters bearing SV40 tumors can be divided into two groups, those that react with both SV40 T and U antigens (T(+)U(+) sera) and those that react with SV40 T antigen only (T(+)U(-) sera). SV40 U-specific sera from monkeys immunized with Ad2(+)ND(1)-infected cells do not react with SV40 T antigen by immunofluorescence but do react with an antigen in the nucleus of SV40-transformed cells and with an early, cytosine arabinoside-resistant antigen present in the nucleus of SV40-infected cells. A heat-stable SV40 antigen detectable by complement fixation with T(+)U(+) hamster sera is present in extracts of SV40-induced hamster tumors and in cell packs of SV40-infected or -transformed cells. SV40 U-antigen synthesis by Ad2(+)ND(1) virus is partially sensitive to inhibitors of deoxyribonucleic acid synthesis, whereas U-antigen synthesis by SV40 virus is an early cytosine arabinoside-resistant event. As an early SV40 antigen differing from SV40 T antigen, U antigen may play a role in malignant transformation mediated by SV40.

Biochemical consequences of type 2 adenovirus and Simian virus 40 double infections of African green monkey kidney cells.

African green monkey kidney (AGMK) cells were nonpermissive hosts for type 2 adenovirus although the restriction was not complete; when only 3 plaque-forming units/cell was employed as the inoculum, the viral yield was about 0.1% of the maximum virus produced when simian virus 40 (SV40) enhanced adenovirus multiplication. The viral yield of cells infected only with type 2 adenovirus increased as the multiplicity of infection was increased. Type 2 adenovirus could infect almost all AGMK cells in culture; adenovirus-specific early proteins and DNA were synthesized in most cells, but small amounts of late proteins were made in relatively few cells. Even when cells were infected with both SV40 and adenovirus, only about 50% were permissive for synthesis of adenovirus capsid proteins. Approximately the same quantity of adenovirus deoxyribonucleic acid (DNA) was synthesized in the restricted as in the SV40-enhanced infection. However, in cells infected with SV40 and type 2 adenovirus, replication of SV40 DNA was blocked, multiplication of SV40 was accordingly inhibited, and synthesis of host DNA was not stimulated. To enhance propagation of type 2 adenovirus, synthesis of an early SV40 protein was essential; 50 mug of cycloheximide per ml prevented the SV40-induced enhancement of adenovirus multiplication, whereas 5 x 10(-6)m 5-fluoro-2-deoxyuridine did not abrogate the enhancing phenomenon.