Cracking the NF-κB code.

The discovery of feedback loops between signaling and gene expression is ushering in new quantitative models of cellular regulation. In a recent issue of Science Signaling, Sung et al. showed how positive feedback downstream of nuclear factor κB (NF-κB) signaling enhances the capacity of macrophages to scale their antimicrobial responses to the dose of pathogen-associated molecular cues. This finding stemmed from analysis of cell-to-cell variability and computational modeling of time integration between signaling and transcriptional responses. Ultimately, such quantitative approaches challenge the oft-assumed time separation of "fast" signal transduction followed by "slow" gene expression, and they provide a better understanding of complex biological regulation over long time scales.