Revision as of 19:48, 5 December 2007

Promoter Kinetics and Stochasticity of Gene Expression

Fast transitions between promoter states is one of the assumptions that has to be fufilled in order for deterministic gene expression models to resemble experimental data (Collins et. al., 2003). This is becuase promoters that remains in an active state allow many "short bursts" of mRNA synthesis; the same rate limiting steps that inhibit turnover time of promoter activation also force the promoter to stay in a repressed state for longer time periods during which production of mRNA is very low.

Diagrams of protein accumulation in genes with slow transition states are characterized by two bistable states that mirror the state of the promoter (Figure 1). This is contrasted with the steady-state concentration of proteins that are expressed by promoters with fast transition kinetics. While most biochemical processes in prokaryotes are assumed to have such a fast turnover rate of promoter state that the effect can be ignored, the kinetics of the expression of some genes are a source of a large amount of variability. The variable number of mRNA synthesis is also reffered to as transcriptional bursting or transcriptional efficiency.