Mathematical Biology seminar Stan Williams Biology Dept., University of Utah "Two beats per measure in cyanobacterial gene expression rhythms " March 30 3:05pm in LCB 121 In the cyanobacterium Synechococcus elongatus the kai genes, A, B and C and the sasA gene encode the core of the circadian timing mechanism essential for circadian clock regulation of global gene expression. Even though thoughtful descriptions have been made regarding the physical interactions, biochemical activities and 3-dimensional structures of these proteins, their specific function as a circadian timing mechanism has not been determined. Here, we describe two ways in which the circadian-clock protein complex regulates global gene expression in this organism. First, we demonstrate differential biochemical interactions among the Kai proteins and the bacterial, two-component-type regulatory protein SasA. Second, we demonstrate large-scale chromosome dynamics as a circadian clock-regulated process that underlies global control of gene expression.