Forum:Genes inhibiting each other's expression

Question

[priya.bmg]

Hi,

Can two genes repress each other's expression?. For example, Gene A inhibits Gene B, Gene B inhibits Gene A. Gene A is a transcription factor goes and binds to the promoter of Gene B and inhibits Gene B expression. Similarly, gene B is a transcription factor, inhibits Gene A expression. So, both Gene A and Gene B are not expressed. Is this mechanism biologically plausible?

Thanks

Answer 1

[i.sudbery]

Yes. This is called a double negative feedback loop. In situations where the inhibition is cooperative (that is, for a doubling in the level of one gene, the level of the other gene more than halves), this circuit forms a bi-stable switch. In a bistable system, only one of the genes can be expressed at once, and which one it is depends on the history of the system (technically, the system has a hysteresis).

Interesting, given how useful they are, such circuits are unrepresented in transcription regulatory networks.

[karl.stamm]

Underrepresented in the networks people have inferred or constructed. Hidden phenomena are hidden.

[i.sudbery]

Perhaps, but their might be other reasons. The requirement for a really good hill coefficient on the repression to properly function as a bistable swtich is difficult to evolve, and without that, you just kind of get an averaging of the expression of the two. However, double negative feedback is over-represented when we talk about a TF and miRNA. One can show that this is because miRNA regulation is inherently non-linear, and so the cooperativity is built in, and thus easier to evolve.

[priya.bmg]

Thank you for the explanation