Based on my RT-qPCR results, this transcription factor functions as an activator under condition A but switches to a repressor under condition B. Interestingly, EMSA assays indicate that under the activator condition, the factor shows decreased binding affinity for its cognate DNA sequence.
What mechanisms could explain such dual functionality? If you know of any similar examples, I would really appreciate your insights. (I cannot provide further details as the data are unpublished.)
Thank you in advance!
Hi Shuxian
An example for such an transcription factor would be Cubitus Interruptus (Ci) in Drosophila. Ci is usually partially degraded by the proteasome - however Ci is not completly degradaded and the remaining part functions as a transcriptional repressor- upon signalling (this is the hedgehog pathway) Ci is not longer degraded and the the full-lenght protein functions as transcriptional activator (homologues are the Gli proteins in vertebrates). However there are other transcription factors with dual functions as activator and repressor e.g. C/EBPß due to differential phopshporylation. Maybe you can check out this article:
Dual-function transcription factors and their entourage
Hello Shuxian,
there are several TFs known to act as activators and repressors.
Some can switch their activity through the binding of a cofactor (e.g. doi: 10.1128/MCB.01754-07) and others behave differently depending on the specific promoter (e.g. doi.org/10.1074/jbc.272.7.4021) .
Yes, this could be happen under certain conditions as a regulatory response to stress conditions.
For example: HsfB1 in tomato which mainly recognized as a repressor but under heat stress can cooperate with activator HsfA1 forming superactive complex and then after recovery retain its repressor function
https://www.researchgate.net/publication/327472461_The_repressor_and_co-activator_HsfB1_regulates_the_major_heat_stress_transcription_factors_in_tomato
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