Cell cycle transition regulation in various organisms.

Cell cycle transition regulatory modules that resemble (in part or whole) the structure of Figure 1 were collected, together with the known information about periodic transcription, the existence of checkpoint and positive feedback regulation. Checkpoint regulation (ChP) and positive feedback loop (PFB) notation: A- acting through activator, I - through inhibitor, B- through both of them. Bold letters note genes that are periodically expressed during the cell cycle [2]. Note that all regulations are by phosphorylation - dephosphorylation reactions, with activators being phosphatases and inhibitors being kinases, except two reverse systems, noted by #. Inh superscript and italic letters for the whole row means the TR is an inhibitor of the cell cycle transition, thus all effects on it are acting with reverse sign to the transition, furthermore an inhibitor of such a transition inhibitor is an indirect activator of the transition. (Detailed discussion and references for all of these findings can be found in File S1).