Rewiring the cell

Micrographs came before movies, and for systems biologists the transition to a dynamic picture seems even more daunting: assembling a global picture of transcription connections in one state was plenty of work already. But now, Nicholas Luscombe, Mark Gerstein (Yale University, New Haven, CT), Madan Babu (MRC, Cambridge, UK), and colleagues have pooled data on multiple growth conditions in yeast. They find that transcriptional connections vary wildly between the states, suggesting that the cell faces a major task when switching from one state to another.

Half of the active interactions (transcription factor to regulated gene) are replaced for every change in condition, and only 66 of 2,476 interactions are retained across 4 or more conditions. The logic of organization also changes depending on whether the cell is responding to purely intracellular changes or to...