Noise Can Induce Bimodality in Positive Transcriptional Feedback Loops Without Bistability

Abstract

Bursty, Infrequent Noise In gene regulatory networks, positive feedback loops can give rise to bistability and hysteresis in gene expression, thereby allowing switching mechanisms and memory effects. To and Maheshri (p. 1142 ; see the Perspective by Levens and Gupta ) eschew the commonly held idea that sigmoidal promoter responses are required to achieve a steady-state bimodal response in a positive feedback loop. Instead, using a model and data from an experiment, they favor noisy gene expression and multiple, noncooperative transcription factor binding as an explanation for the bimodal response, and they expect that similar noisy systems are widespread in biology.