Principal Investigators

Robert (Tij) Tjian

UC Berkeley Faculty Page
HHMI Research Abstract



Robert Tjian is a professor of biochemistry and molecular biology at the University of California, Berkeley. Trained as a biochemist, he has made major contributions to the understanding of how genes work during three decades at Berkeley. He was named an HHMI investigator in 1987 and served as president of the Howard Hughes Medical Institute from 2009 until 2016.

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.

Early transcription model drawn by Tij.
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.

Xavier Darzacq

UC Berkeley Faculty Page 



Xavier Darzcaq did his Ph.D with Dr. Tamas Kiss at the University of Toulouse were he discovered the first function of Cajal bodies. Whereas his university and PhD studies were more orientated toward biochemistry and cell biology, he decided in 2002 to join the Laboratory of Dr. Robert Singer at the Albert Einstein College of Medicine to be trained in light microscopy techniques for single molecule imaging in live cells, in one of the most renowned laboratories in the world. The reason behind this choice was to acquire a new technology that complements his other experimental competences and allows him to directly “look” at single-molecule events inside a cell.

The Cajal body is a nuclear structure where small nuclear RNAs go for modification.

During his post-doctoral studies, he developed imaging technologies using genetically encoded fluorescent tags to follow transcription. These biosensors of genetic expression are used to dissect the kinetics of RNA polymerase II within its natural nuclear environment.  Xavier then moved to Olivier Bensaude’s Lab at IBENS (Paris), were he spent two years.

In 2008, Darzcaq set up his own team at IBENS to study how chromatin structure and nuclear architecture regulate transcription. In 2014 he relocated his group to UC Berkeley in California. He currently focuses on the implementation of new technologies to the field of imaging single molecules in live single cells and full embryos. Recent findings suggest a very strong link between the organization of the nucleoplasm and the biophysical rules governing transcription factor assemblies.