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I know that DNA binding transcription factors are trans-acting, but what about general transcription factors? Are they cis or trans acting?

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  • $\begingroup$ Hi there and welcome to biology.se. For this site users are expected to do a little background reading before asking a question. What sources have you looked at that lead to this question? $\endgroup$
    – James
    Nov 19, 2015 at 2:43
  • $\begingroup$ From Wikipedia: A defining feature of transcription factors is that they contain one or more DNA-binding domains (DBDs), which attach to specific sequences of DNA adjacent to the genes that they regulate. So, there's no differentiation between "DNA-binding transcription factors" and "general transcription factors". In order to be classified as a TF, a protein must be capable of directly binding DNA. $\endgroup$
    – MattDMo
    Nov 20, 2015 at 15:46

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When we say trans we mean that a diffusible factor, or agent is involved. So a molecule synthesized at one location, that can have a regulatory role in another location in the cell is said to be a "trans-acting" factor.

When we say cis we mean physically linked to, in such a way that the biological regulation only affects other molecules that are attached (in other words, something that is "cis-acting" cannot be freely diffusible).

So prokaryotic operators or promoters, and eukaryotic enhancers and promoters would be examples of cis-acting sequences, or elements. All protein transcription factors, or even DNA-binding proteins, are therefore trans-acting.

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General transcriptional factor complexes bind to DNA at promoters of genes via DNA binding proteins such as TATA-binding protein.

It is quite clear that it is trans-acting.

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  • $\begingroup$ I agree, all transcription factors are trans-acting. I just am not sure that I agree with you first sentence completely. Some of the proteins bind to other proteins and don't themselves have a DNA binding domain. I might be wrong in the sense that these proteins may not be canonically considered TFs, but they do exist. $\endgroup$
    – AMR
    Nov 19, 2015 at 3:47

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