For the ICRF Annual Report, 1979: III. Co-Transfection with Papovavirus and Retrovirus DNA Using Recombinant DNA Prepared
Varmus here provided an overview of his research during his sabbatical year at the Imperial Cancer Research Fund in London
in 1978-79. His studies focused on the ways in which retroviruses cause mutations of genes, including the genes deposited
by other retroviruses that had previously infected the cell.
Item is a photocopy.
Number of Image Pages:
1 (81,149 Bytes)
Original Repository: University of California, San Francisco. Archives and Special Collections. Harold E. Varmus Papers
Reproduced with permission of the Regents of the University of California.
Medical Subject Headings (MeSH):
Retroviruses and the Genetic Origins of Cancer, 1970-1993
For the ICRF Annual Report, 1979: I. The Rare Revertants of an ASV-Transformed Rat Cell Have Lost Proviral DNA or Bear Mutations
in SRC (1979)
For the ICRF Annual Report, 1979: II. Retroviruses as Mutagens: Isolation of Revertants with Deletions and/or Insertions in
the ASV Provirus in B31 Cells after Superinfection with MuLV (1979)
The introduction of purified pieces of functionally interesting DNA into eukaryotic cells is an important means to deciphering
genetic regulation in higher organism. In many cases, the DNA of interest does not encode functions for which genetic selection
procedures are available. We have developed a procedure for circumventing this difficulty by linking transforming regions
of a papovavirus genome to pieces of retroviral DNA lacking selectable markers. The approach has the additional virtues of
not requiring expression of the retrovirus DNA and of allowing an assessment of signals thought to be important in the integration
and expression of the two types of viral genomes.
We joined two fragments of polyoma virus DNA, which together contain an intact early region, and a fragment of transformation-defective
avian sarcoma virus (ASV) DNA, which contains the env gene of ASV and sequences from the termini of viral RNA. (The ASV DNA
was provided by Dr. W. DeLorbe of the University of California, San Francisco, after cloning in [lambda]gt WES.) The desired
recombinant molecule was isolated as a linear species from other products of ligation of the three fragments by digestion
with the restriction endonuclease BamHI and preparative gel electrophoresis. After confirming the structure of the recombinant
DNA, it was used to transfect rat-1 cells with the calcium phosphate technique. Most of the resulting transformed cells contained
from 1 to 3 copies of recombinant DNA. Napping studies indicated that the recombinant molecules did not circularize during
transfection, since the integrated copies were approximately co-linear with the transfecting DNA, though lacking small regions
from the termini of the recombinant molecules. Preliminary analysis of the ASV-specific RNA in several transformed lines
indicates that few or no stable transcripts are synthesized from this region of the recombinant DNA's (tests performed
by S. Ortiz, University of California, San Francisco). The significance of these observations with respect to signals for
integration and expression of retroviral DNA is being evaluated by application of these methods to other combinations of molecules
and host cells.