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.