Robert Tjian has been president of the Howard Hughes Medical Institute since April 2009. Trained as a biochemist, he has made major contributions to the understanding of how genes work during three decades on the faculty of the University of California, Berkeley. He was named an HHMI investigator in 1987.

Tjian studies the biochemical steps involved in controlling how genes are turned on and off, key steps in the process of decoding the human genome. He discovered proteins called transcription factors that bind to specific sections of DNA and play a critical role in controlling how genetic information is transcribed and translated into the thousands of biomolecules that keep cells, tissues, and organisms alive. Tjian's laboratory has illuminated the relationship between disruptions in the process of transcription and human diseases such as cancer, diabetes, and Huntington's. More recently, he has begun studying how transcription factors control the differentiation of embryonic stem cells into muscle, liver, and neurons.

Tjian received a bachelor's degree in biochemistry from Berkeley in 1971 and a Ph.D. from Harvard University in 1976. After completing a postdoctoral fellowship at the Cold Spring Harbor Laboratory with James Watson, he joined the Berkeley faculty in 1979. At Berkeley, Tjian assumed a variety of leadership roles, including spearheading a major campus initiative to support and implement new paradigms for bioscience teaching and research. He served as the Director of the Berkeley Stem Cell Center, and the Faculty Director of the Li Ka Shing Center for Biomedical and Health Sciences. He is a member of the National Academy of Sciences and has received many awards honoring his scientific contributions, including the Alfred P. Sloan Prize from the General Motors Cancer Research Foundation and the Louisa Gross Horwitz Prize from Columbia University. He was named California Scientist of the Year in 1994.

Tjian remains an active scientist. His small laboratory group at HHMI's Janelia Farm Research Campus focuses on the development of new approaches to image biochemical activities in single living cells. He also maintains a research laboratory at UC Berkeley, where he is a professor of biochemistry and molecular biology.