title: Complementation between SV40 and RFV defectives and acquisition of SV40 origins by late RFV genomes.
abstract: EL SV40 and RFV are variants of SV40 and BKV which contain bipartite or dual genomes. One molecule contains all the early viral sequences (E-SV40, E-RFV) and the other all the late viral sequences (L-SV40, L-RFV). Early and late genomes complement one another during productive infection. Experiments were designed to determine if E-genomes of one virus could complement L-genomes of another virus. If complementation did occur, intermolecular recombination events which lead to a more efficient infection or an altered host range might occur, and the sequences involved could than be identified. Two combinations were generated by direct transfection of BSC-1 green monkey cells. E-RFV and L-SV40 DNA complementation resulted in hybrid virus growth and cell killing. The hybrid demonstrated a narrow host range. Following serial passage, some E-RFV genomes contained SV40 origin region sequences but these recombinants did not overgrow prototype E-RFV genomes, even after many virus passages. In addition, no significant alterations in host range could be detected. Complementation between E-SV40 and L-RFV yielded a virus with a relatively wider host range. Virus growth and cell killing appeared very slowly at first. However, with each passage of E-SV40/L-RFV, cell killing occurred progressively more rapidly, until passage 7 when it became extensive in 7 days rather than 6-8 weeks. Infected cells contained 10-20 times more E-SV40 than L-RFV DNA during the first passage. However, by passage 7, both genomes were equally represented. During serial passage, L-RFV DNA acquired SV40 sequences from around the origin and the terminus of replication, such that recombinant (r) L-RFV genomes contained three SV40 origins [corrected] (including the 72-bp repeat) and 2 termini, and prototype L-RFV DNA was lost. E-SV40/rL-RFV demonstrated an altered host range propagating in some cell lines which did not support E-SV40/L-RFV growth. Both the host range change and the increased growth of rL-RFV genomes were shown to be at least partly caused by the acquisition of the SV40 sequences.
mesh_terms: D000818:Animals; D001739:BK Virus / Q000235:genetics* / Q000502:physiology; D002460:Cell Line; D003001:Cloning, Molecular; D003588:Cytopathogenic Effect, Viral; D004262:DNA Restriction Enzymes; D003673:Defective Viruses / Q000235:genetics*; D005814:Genes, Viral; D005816:Genetic Complementation Test; D009693:Nucleic Acid Hybridization; D011120:Polyomavirus / Q000235:genetics*; D011995:Recombination, Genetic; D013539:Simian virus 40 / Q000235:genetics* / Q000502:physiology; D014162:Transfection
chemical_list: D004262:DNA Restriction Enzymes