Post-doc with Yarmolinsky (NCI-Frederick)
My post-doctoral work was at NCI-Frederick Cancer Research Center with Michael Yarmolinsky, who, upon returning from France wanted to be at NIH, not boondocks Frederick in the Basic Research Program. This was a P1 lab. P1 bacteriophage was unique in packaging bacterial DNA and facilitating transfer to recipient strains. It provided a unique mechanism for facile genetic manipulations. The lab was full of stars, including a brilliant Nat Sternberg who developed the Lox-Cre system for bacterial and then mammalian genetic manipulations. It was a joke based on lox and cream cheese, but an acronym for locus of recombination, which is what it targeted genetically. My project was to create a recombinant SOS response assay based on lambda phage induction, using a reporter gene, and to demonstrate how “easy” it was to detect DNA damaging agents. It was designed to compete with Ames’ new mutagenicity assay. This was among the first uses of lacZ as a reporter, it’s expression dependent on lambda phage induction, an SOS response. The genetic strategy was laid out for me and I was expected to implement it. I succeeded after an unhappy 2 years. At the end, I had finally learned enough to converse somewhat on their level. Later I called it the BIA (Biochemical Induction Assay). It’s published in the inaugural issue of the EMS journal, EMM Volume 1 (Elespuru and Yarmolinsky 1979). After Bruce Ames declined to accept it for PNAS, he suggested the new EMS journal. How naïve to expect that Ames would accept such a viable competitor. It had much to recommend it, including a single bacterial strain to detect multiple types of DNA damage, and an elapsed time of 4 hours between test initiation and final results.
I spent a lot of time with this assay in subsequent years, discussed briefly later. Quillardet and Hofnung copied our methods and published a nearly identical assay using a different SOS response endpoint,sfi , creating the SOS Chromotest, 3 years later. They even copied our method of calculating enzymes units as the endpoint. Errol Zeiger said he reviewed the Quillardet paper for Mutation Research and told Fritz Sobels they had to cite our work, but they didn’t. They created a commercial assay and promoted it relentlessly. However, I knew from my own work that the SOS assay misses some types of DNA damage, especially missense mutagens. Also, by commericializing the assay they couldn’t compete with Ames, who gave away his bacterial strains. Nevertheless, you might say I had some recompense in the end by publishing a paper in Science using the assay. It was actually terrific for high school science projects. The results were seen the same day, color developing as from a polaroid film. This was exciting for students. I think such a rapid assay could still be useful in certain contexts.