Suzanne Bourgeois, PhD, had a knack for finding things that others had overlooked. In the 1960s, when the molecular machinery behind gene regulation was still largely a mystery, she identified something no one had proved before: that the protein responsible for switching a gene off was real, measurable, and could be studied in precise detail. As the founder of Salk’s Regulatory Biology Laboratory, Bourgeois studied the regulation of gene expression—the process cells use to turn genes “on” or “off”—using the bacterial lactose (lac) operon as a model system. In the 1960s, when little was known about the circuit, Bourgeois demonstrated that the lac repressor was a protein. She used the system to characterize, for the first time, the interaction between a regulatory protein and DNA. She later studied gene regulation in animal cells and eventually identified compounds that could help reverse multidrug resistance in cancer. From that foundation, Bourgeois went on to ask bigger questions, eventually identifying compounds with the potential to help overcome one of cancer treatment’s most stubborn problems: the ability of tumors to resist multiple drugs at once. Her National Institutes of Health research grant funding continued through 1994, a telling measure of how seriously the scientific…