Various types of transcription factor based genetic oscillators.

<p>In case of positive regulation the combinatorial transcription factors bound at <i>cis</i>-regulatory modules enhance the initiation of transcription by strengthening the RNAPII-promoter interactions through their distal action (positive arrows) whereas in case of negative regulation, the RNAPII-promoter complex will be destabilized by the combinatorial TFs present at CRMs (negative arrows). <b>A</b>. Goodwin-Griffith oscillator. <b>B1</b>. One-to-one dual feedback oscillator. Here the end-product of TF gene A binds at the promoter of TF gene B and down-regulates it whereas the end-product of TF gene B binds with the promoter of TF gene A and down-regulates it. <b>B2</b>. Two independent Goodwin-Griffith oscillators are coupled through -OR- type logic with NN-NN configuration. Here the promoter of TF gene A will have binding sites for the end-products of both TF gene A and B and so on for TF gene B. <b>B3</b>. GG oscillators are coupled through -AND- type logic with N-N configuration. <b>B4</b>. GG oscillators are coupled through -OR- type logic with NN-PP configuration. <b>B5</b>. GG oscillators are coupled through -OR- type logic with NP-NP configuration. <b>B6</b>. Possible robust synthetic gene oscillator. Here K is the booster TF gene that is coupled to N-N type dual feedback oscillator via –OR- gate. <b>C1</b>. Repressilator that is built with three TF genes by cyclic coupling. <b>C2</b>. Three independent Goodwin-Griffith modules are coupled through -OR-type logic. Here dashed lines show the fully interconnected network. <b>C3</b>. Three independent Goodwin-Griffith modules with -AND-type logic. Here dashed lines show the fully interconnected network.