Howard Varmus
In the late 1960’s, while taking night classes at the NIH, Howard Varmus would be captivated by the partnership that seemed to exist between viruses and cancer. His interests would be further spurred by the introduction of two opposing hypotheses, the provirus hypothesis and the virogene-oncogene hypothesis, both attempted to describe how RNA viruses interacted with chromosomes of infected cells, but had little sound data to back either up. With this information in hand, Varmus, in the summer of ’69, travelled to UC San Francisco where he alongside Mike Bishop would launch their study of the avian sarcoma virus and its transforming properties. Before they could begin their studies however, two more very important discoveries were made. The
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They then hybridized these cDNA fragments to a td deletion mutant and submitted it to HAP chromatography to eliminate the hybridized dsDNA, resulting in the isolation of the transforming (sarc) gene. The isolated cDNAsarc was found to be 1600 nucleotides in length, which was deemed an adequate length to code for a protein with the ability to transform infected cells. Now with the cDNAsarc probe in hand, the experimenters sought to find sequence homology between the sarc probe and several avian species genomes’ (chicken, turkey, quail, duck, and emu). In the experiment, as seen in fig 1 and table 1, the rate of association between avian DNA and (_^3)H-labeled cDNAsarc competing against (_^14)C-labeled unique sequences purified from chicken DNA was measured by hydrolysis of ssDNA by the S1 nuclease. The results showed significant rates of annealing for all avian species tested, except for the emu. The experimenters speculated that this low rate of annealing could be attributed to the distant ancestry between the emu and the others birds tested, which would result in a divergent form of the cellular sarc gene. To account for this a less stringent measure of duplex formation, HAP fractionation, was utilized and resulted in rates similar to those found in the birds tested with the S1 nuclease. From this information Varmus and Bishop
They then hybridized these cDNA fragments to a td deletion mutant and submitted it to HAP chromatography to eliminate the hybridized dsDNA, resulting in the isolation of the transforming (sarc) gene. The isolated cDNAsarc was found to be 1600 nucleotides in length, which was deemed an adequate length to code for a protein with the ability to transform infected cells. Now with the cDNAsarc probe in hand, the experimenters sought to find sequence homology between the sarc probe and several avian species genomes’ (chicken, turkey, quail, duck, and emu). In the experiment, as seen in fig 1 and table 1, the rate of association between avian DNA and (_^3)H-labeled cDNAsarc competing against (_^14)C-labeled unique sequences purified from chicken DNA was measured by hydrolysis of ssDNA by the S1 nuclease. The results showed significant rates of annealing for all avian species tested, except for the emu. The experimenters speculated that this low rate of annealing could be attributed to the distant ancestry between the emu and the others birds tested, which would result in a divergent form of the cellular sarc gene. To account for this a less stringent measure of duplex formation, HAP fractionation, was utilized and resulted in rates similar to those found in the birds tested with the S1 nuclease. From this information Varmus and Bishop