Dynamic nutrient feeding to control glutamine at low levels in protein-free fed-batch cultures of 293-human embryonic kidney (HEK) cells achieved cell concentrations of 6 x 10(6) cells/ml. This represented a 4-fold improvement in cell concentration compared to batch cultures. Reduction in glutamine and glucose consumption, as well as lactate and ammonia production, were also observed in these fed-batch cultures. High virus production titers of 3 x 10(11) pfu/ml were achieved in fed-batch cultures which were 10,000-fold higher than batch cultures. An investigation of the transcriptional regulation of the metabolic changes associated with the batch and the low-glutamine fed-batch cultures using DNA microarray was conducted. This analysis provides better understanding of the transcriptional regulatory mechanism resulting in the observed physiological changes. Transcriptional profiling of cells from the mid-exponential, late exponential and stationary phases of both the batch and fed-batch were undertaken using an 18,000 element human chip. Transcriptional profiles were ontologically classified to provide a global view of the genetic changes. Furthermore, a pathway-oriented analysis focusing on cellular metabolism was conducted to reveal the dynamic regulation of genes related to amino acid metabolism, tRNA synthetases, TCA cycle, electron transport chain and glycolysis.