Fitting Experimental Transcription Data with a Comprehensive Template-Dependent Modular Kinetic Model

In the companion article, we developed a modular scheme for representing the kinetics of transcription elongation by RNA polymerase. As an example of how to use these approaches, in this article we use a comprehensive modular model of this sort to fit experimental transcript elongation results obtained on the canonical tR2 template of phage λ by means of complementary bulk gel electrophoresis and surface plasmon resonance assays. The gel electrophoresis results, obtained in experiments quenched at various times after initiation of transcription, provide distributions of RNA lengths as a function of time. The surface plasmon resonance methods were used to monitor increases and decreases in the total mass of transcription elongation complexes in the same experiments. The different measures of transcription dynamics that these methods provide allow us to use them in combination to obtain a set of largely robust and well-defined kinetic parameters. The results show that our modular approach can be used to develop and test predictive kinetic schemes that can be fit to real transcription elongation data. They also suggest that these approaches can be extended to simulate the kinetics of other processes that involve the processive extension or shortening of nucleic acid chains and related systems of sequential branching reaction events.