As a college student in the 1960s, Joan Steitz never imagined herself as a top-flight scientist. Certainly, she was fascinated by science. She even assisted senior scientists in laboratories at the Massachusetts Institute of Technology, where she was befriended by James D. Watson, co-discoverer of the DNA double helix, and at the Max Planck Institute in Germany. But when it came time to choose a career path, Steitz had convinced herself that she was not devoted enough to research to spend grueling nights and weekends in the laboratory.
What's more, she was discouraged by the lack of female role models working as senior scientists and full professors. "When I was a graduate student, there were no women professors in the biological sciences at any major university," Steitz recalled. "Consequently, I never envisioned myself being where I am today: I never thought I would teach; I never thought I would mentor graduate students; I never thought I would be on the faculty of a prominent university. I really thought I would be a research associate in someone's lab—a man's of course."
So instead, she applied to medical school and was accepted by Harvard. And she almost went. After graduating from college, though, Steitz took a summer job in another laboratory, this one at the University of Minnesota, under the supervision of cell biologist Joseph Gall. He set up Steitz with her own research project to determine whether ciliary basal bodies from the protozoan Tetrahymena pyriformis contain nucleic acid—a reasonable question since mitochondria had just been shown to possess their own complement of DNA.
Suddenly, Steitz found herself working nights and weekends. By August, and with Gall's encouragement, she had decided that she really was not interested in caring for sick people and wanted to change her plans. Fortunately, a prospective student in Harvard's graduate program in biochemistry and molecular biology had decided not to enter the program, and with Watson's help, Steitz was allowed to take the open slot.
In 1963, she became the sole woman in a class of 10 to begin graduate studies in biochemistry and molecular biology at Harvard, and the first female graduate student to work under Watson's guidance. "He was an excellent mentor and very supportive of my work," said Steitz, whose early work focused on RNA structure and function in bacteria. "He was truly an inspiration and taught me to focus on the important questions in science."
Today, Steitz is best known for discovering and defining the function of small nuclear ribonucleoproteins (snRNPs), which occur only in higher cells and organisms. These cellular complexes play a key role in the splicing of pre-messenger RNA, the earliest product of DNA transcription. Both DNA and pre-messenger RNA typically contain numerous nonsense segments called "introns." Working in the nucleus, snRNPs excise the introns from pre-mRNA and splice together the resulting segments, which together make up messenger RNA. The mRNAs contain the "recipes" for making proteins, which are critical for carrying out all of the body's most basic biological processes.
Steitz's research may yield new insights into the diagnosis and treatment of lupus, an autoimmune disease that develops when patients make antibodies against their own DNA, snRNPs, or ribosomes, the body's protein-making factories. She and her colleagues are also studying other snRNPs involved in excising a rare, divergent class of introns and still other snRNPs involved in pre-ribosomal RNA processing.
Steitz is married to HHMI Investigator Thomas Steitz, the Sterling Professor of Molecular Biophysics and Biochemistry and Professor of Chemistry at Yale University. Although they share general areas of research interest, the two have coauthored only one paper, in 1993, on the mechanistic aspects of RNA catalysis in splicing. Having a spouse who understands "the pressures and joys of a career in academic science makes it all possible," Steitz said.
