Noncommutative Biology: Sequential Regulation of Complex Networks
Fig 1
Combinatorial logic bottlenecks information flow in networks.
(A) The number of ways that three TFs (K1, K2, K3) can be ON or OFF (tabulated at right) is the same as the number of ways they can bind at promoters (left). An equal number of gene expression states are observed whether the TFs use AND logic (requiring all factors be present) or OR logic (requiring at least one of the factors). (B) Signal-to-target information flow is bottlenecked by regulators if (i) the regulators respond to multiple targets, or (ii) the signals activate multiple regulators. The allowed target states are tabulated for signals using AND logic and regulators using AND/OR logic. (C) A feedback loop causes constitutive activation of a regulator (K1) and leads to fewer accessible configurations (tabulated at right).