Optimizing information flow in small genetic networks. III. A self-interacting gene

TL;DR

This paper investigates how self-regulation in simple genetic networks optimizes information transfer, revealing that moderate self-activation or repression enhances steady-state gene expression control without causing bistability.

Contribution

It provides a detailed analysis of self-regulatory gene circuits, identifying optimal parameter regimes for information transmission in steady state conditions.

Findings

Nonzero self-regulation levels are generally optimal.

Self-activation is favored at low transcription factor concentrations.

Self-repression is favored at high concentrations.

Abstract

Living cells must control the reading out or "expression" of information encoded in their genomes, and this regulation often is mediated by transcription factors--proteins that bind to DNA and either enhance or repress the expression of nearby genes. But the expression of transcription factor proteins is itself regulated, and many transcription factors regulate their own expression in addition to responding to other input signals. Here we analyze the simplest of such self-regulatory circuits, asking how parameters can be chosen to optimize information transmission from inputs to outputs in the steady state. Some nonzero level of self-regulation is almost always optimal, with self-activation dominant when transcription factor concentrations are low and self-repression dominant when concentrations are high. In steady state the optimal self-activation is never strong enough to induce bistability, although there is a limit in which the optimal parameters are very close to the critical point.