Dr. Crooke, professor and chair of the department of biochemistry and molecular biology, studies two areas of cellular biology. One is to determine molecular mechanisms that cells employ to assure that their genome is faithfully replicated once, and only once, per cell cycle. Loss of such mechanisms is one of the hallmarks of the onset of carcinogenesis. The second project in Dr. Crooke's laboratory focuses on understanding the physiological role that cellular polyphosphates play in how cells respond to environmental stresses. These long, energy-rich polymers are found found in virtually all organisms. Disruption of the gene that encodes the polyphosphate biosynthetic enzyme, polyphosphate kinase (PPK), gives rise to cells that have decreased viability following exposure to environmental challenges such as heat, UV-irradiation and oxidativestress, or when the cells are maintained in the stationary phase for prolonged periods. Certain mutations elsewhere in the genome have the ability to suppress the sensitivities that ppk knock-out cells have toward these environmental stresses. Identification of the genes that harbor such mutations will help us understand in which signal transduction and stress response pathways polyphosphates participate.