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Operons and DNA replication

  1. Feb 10, 2010 #1
    How do operons interfere with DNA replication, if at all?

    I know, for example, that repressors can stop RNA polymerase, keeping a segment from being transcribed, but it's still replicated. How is this?
    My guesses are:
    A. The enzymes involved in DNA replication can run right over them.
    or
    B. All operons are temporarily activated during DNA replication.

    Or, of course, something completely different...

    Any help is appreciated!
    Thanks.
     
  2. jcsd
  3. Feb 11, 2010 #2
    Not all operons are regulated by repressors. In other words, the absence of repressors does not automatically make an operon active. During DNA replication, the single stranded DNA is bound with single strand binding proteins, which probably prevents the RNA synthesis by RNA polymerases (even if activators and other required stuff were there to promote the synthesis).. And when the DNA polymerase has created the complementary strand, then the repressors probably are the first to bind the DNA, preventing unwanted RNA synthesis. However, it is known that even suppressed operons "leak" a bit.. So potentially some RNA synthesis may occur during DNA replication.. But I'm just speculating here since this is not my expertise.
     
  4. Feb 11, 2010 #3

    Ygggdrasil

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    Science Advisor

    This question, of how the DNA replication machinery bypasses proteins bound to DNA, is an active field of research and we are still learning how the process works. It seems like DNA polymerases are able to kick the proteins off of DNA (for example see http://www.physorg.com/news185010534.html), although the details of how this occurs is not yet well understood.

    Now something to keep in mind here is that it is difficult to get DNA and RNA polymerases started (both require specialized factors that bind to the DNA, open up the DNA, recruit the polymerases, and position them in order to get started), but once they get going, they are fairly efficient. Therefore, a protein that needs to block the difficult transcriptional initiation step (for example, by interfering with the proteins that recruit RNA polymerase to the DNA) will not necessarily be able use the same mechanisms to block a DNA or RNA polymerase that has already initiated.
     
  5. Feb 15, 2010 #4
    Thank you both for your responses!

    Yea, I do know about positive and negative inducible and repressible operons, I just dealt with repressors for simplicity's sake.

    Ygggdrasil, thanks for the link!
     
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