gene expression and alternative sigma factors

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neon
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gene expression and alternative sigma factors

Post by neon » Tue Jun 13, 2006 9:20 am

Hello...Calling all transcription experts,

Can you answer me this question please?

I understand that the presence of alternative sigma factors allows for the activation of different regulons, and this is used in the many stress responses (e.g. of e.coli)

But, on the genome, can operons induced by the holoenzyme incorporating one sigma factor overlap those that are activated as the result of another sigma factor? If not, why not, and if yes, then what happens?

And for good measure, here is another question:

What happens if a promotor motif is incorporated within an operon? Surely this can happen, as the pribnow box etc. are not that specific. How would the holoenzyme know not to bind in the middle of 'another' operon?

I look forward to your replies.

neon

PS. It is most helpful if you can indicate how certain you are of your responses - i.e. if you are guessing what you are saying is the case, please state this! If you are the leading expert on the subject, then please tell me so - this makes it more useful for me....

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