Efficiency and versatility of distal multisite transcription regulation

TL;DR

This paper presents a computational model that accurately predicts transcription rates in complex DNA looping systems like the lac operon, revealing how multiple operators enable both robust repression and sensitive induction.

Contribution

A scalable quantitative approach to analyze multisite DNA looping regulation, providing insights into the balance of repression and induction in genetic switches.

Findings

Model predicts transcription rates over five orders of magnitude.

Three operators enable robust repression and sensitive induction.

Accurately accounts for all operator deletion mutants.

Abstract

Transcription regulation typically involves the binding of proteins over long distances on multiple DNA sites that are brought close to each other by the formation of DNA loops. The inherent complexity of the assembly of regulatory complexes on looped DNA challenges the understanding of even the simplest genetic systems, including the prototypical lac operon. Here we implement a scalable quantitative computational approach to analyze systems regulated through multiple DNA sites with looping. Our approach applied to the lac operon accurately predicts the transcription rate over five orders of magnitude for wild type and seven mutants accounting for all the combinations of deletions of the three operators. A quantitative analysis of the model reveals that the presence of three operators provides a mechanism to combine robust repression with sensitive induction, two seemingly mutually exclusive properties that are required for optimal functioning of metabolic switches.