Question

Positive feedback: What is the effect of positive auto-regulation on the response time? Use as a model the following linear equation: dX / dt = β + β1 X –α X Explain each term and solve for the response time. When might such a design be biologically useful?

Autoregulated cascade: Gene X encodes a repressor that represses gene Y, which also encodes a repressor. Both X and Y negatively regulate their own promoters. (a) At time t=0, X begins to be produced at rate β, starting from an initial concentration of X=0. What are the dynamics of X and Y? What are the response times of X and Y? Assume logic input functions, with repression thresholds Kxx, Kxy for the action of X on its own promoter and on the Y promoter and Kyy for the action of Y on its own promoter. (b) At time t=0, production of X stops after a long period of production, and X concentration decays from an initial steady-state level. What are the dynamics of X and Y? What are the response times of X and Y?

Answer 1

Auto-regulation is the phenomenon in which some genes are regulated by their own product. Autoregulation is of two types namely positive auto-regulation and negative autoregulation.

In positive autoregulation, the transcription factor X activates its own expression when binding to its promoter. Dynamics of X using linear equation is as follows:

Autoregulated cascade:

It is given that gene X and Y negatively regulate their own promoters. Both X and Y encodes repressors and the gene X represses gene Y.