Susan Golden (née Stephens) is a Professor of molecular biology known for her research in circadian rhythms. She is currently a faculty member at UC San Diego.
Golden was born in Pine Bluff, Arkansas in 1957. She attended the local public high school, where she was involved with the marching band and school newspaper. She was accepted to the Mississippi University for Women in 1976 as a journalism major, but soon switched her studies to major in biology and minor in chemistry.
Golden graduated from MUW in two years, after which she was offered a position in the first cohort of trainees in a NIH-financed doctoral program in genetics at the University of Missouri. During her graduate program, Golden met James Golden, a fellow doctoral student. They later married in 1979. At the University of Missouri, Golden researched the protein makeup of the photosynthetic center in cyanobacteria, work she continued when she moved to the University of Chicago in 1983 as a postdoctoral research fellow.
In 1986 Golden accepted a faculty position at Texas A&M to further her investigation into light-dependent gene regulation in bacteria. While at Texas A&M, Golden became interested in studying circadian rhythms after her first encounter with Carl H. Johnson and Takao Kondo, with whom she would go on to discover the Kai complex. Golden was promoted to Distinguished Professor at Texas A&M in 2003, and then moved to UC San Diego in 2008 where she is currently a Distinguished Professor and the Director of the Center for Circadian Biology.
Research contributions
Early work
Golden began her graduate career with Louis A. Sherman, where she used genetics to research the proteins in photosynthetic complexes of the cyanobacteria Synechoccus elongatus. Golden was the first to demonstrate that a mutant allele of the psbA gene is sufficient to confer herbicide resistance in cyanobacteria. Other research later confirmed that this gene coded for a protein integral to the Photosystem II complex involved in photosynthesis. These findings also demonstrated that genetic manipulation of cyanobacteria was relatively simple, opening up S. elongatus as a model organism for future genetic experiments. During her postdoctoral research at the University of Chicago, in the lab of Robert Haselkorn, Golden continued to work on developing genetic manipulation techniques for Synechoccus elongatus in order to elucidate mechanisms of gene regulation in photosynthesis genes. In 1989, Golden's team discovered that the specific psbA allele expressed by cyanobacteria depended on the lighting conditions in which the colony was grown. This finding led her to investigate more generally how light influences expression of photosynthetic genes in the organism and contributes to the overall understanding of bacterial responses to environmental input. This line of inquiry necessitated the development of a technique for visualizing changes in gene expression in living organisms. During her time as a professor at the Texas A&M, Golden attempted to solve this problem by attaching a luciferase gene to the promoters of the cyanobacterial genes of interest and viewing the colonies with a night vision scope. The approach was a success, allowing for quantification of cyanobacterial gene expression in vivo over an extended time period. This technique drew the interest of chronobiologist Carl H. Johnson, with whom Golden would go on to collaborate and eventually discover the KaiABC complex .
Discovery of kai complex
Golden studies the endogenous rhythms of cyanobacteria, a group of photosynthetic bacteria known to have circadian clocks. She transformed Synechococcus elongatus, one of the better studied cyanobacteria species, with a luciferase reporter gene and showed circadian rhythm in bioluminescence. This reporter system was used to discover three key proteins related to the cyanobacterial clock: KaiA, KaiB, and KaiC. In collaboration with Carl H. Johnson and Takao Kondo, she demonstrated and described the molecular mechanism regulating circadian rhythms in S. elongatus PCC 7942, the only model organism for a prokaryotic circadian clock. Susan Golden identified genes in the S. elongatus genome that contribute to circadian rhythm through mutational screens using transposons to disrupt genes and their function. In one mutation screen study, nineteen mutations were identified and mapped to the three kai genes; Inactivation of any single kai gene reduced kaiBC-promoter activity and abolished the circadian rhythm of expression of KaiA and KaiB.