DNA damage

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shirkan
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DNA damage

Post by shirkan » Mon Jan 01, 2007 1:35 pm

hi
I was wondering if some proteins have a role of physically protecting DNA from damage (UV, ROS...). That is does their physical connection with DNA protect it somehow?
thanks

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sachin
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Post by sachin » Mon Jan 01, 2007 1:42 pm

Not proteins but enzymes do...... eg Topoisomerase.
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sachin
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Post by sachin » Mon Jan 01, 2007 3:05 pm

Histone is one that helps to coil DNA and make it resistant to mechanicle and unwanted chemical action...
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shirkan
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Post by shirkan » Mon Jan 01, 2007 3:25 pm

does it protect DNA against external DNA damaging agents like UV radiation or free radicals? Does this mean that DNA is damaged only where it is uncoiled?

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G-Do
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Post by G-Do » Tue Jan 02, 2007 2:15 am

The cell can protect itself (meaning all of its molecules, not just DNA) from radical oxygen species using superoxide dismutases, which target R.O.S.s for de-radicalization. Ascorbic acid (vitamin C) also helps. I'm not sure if the cell has preventive measures for pre-emptively protecting itself from U.V. radiation.

DNA damage - including double-stranded breaks - can be repaired by agents of the DNA damage response pathway. Many models of this pathway involve detection of DNA damage by ATM/ATR, a signal transduction through p53, and the activation of repair enzymes.

Hope that helps!

EDIT: Oh, I see what you're saying now. Well, there is some evidence to suggest that the telomeres are protected from DNA damage of all stripes by so-called "cap" complexes - protein multimers that bind to the telomeres. And several DNA-binding proteins - including histones - can protect DNA from the action of endonucleases. This is the theoretical basis for a "DNase protection assay." But I can't remember whether there are any general purpose "protector" proteins that physically bind DNA and protect it from U.V. light or R.O.S.s in the genome proper, sorry.

Rather, I think the way the cell deals with these mutagens is to try to correct DNA damage after the fact. The reason for this is that proteins can be damaged by U.V. light and R.O.S.s, too, so it is difficult to conceive of a way to use them to "shield" a piece of DNA. Most of the literature I have read on this subject deals with preventive measures against oxidative stress and DNA damage repair, so if anyone knows better, please chime in.
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sachin
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Post by sachin » Tue Jan 02, 2007 4:22 pm

So therfore we do not have any protein that avoids damage by UV, Radiations........

Only we have to depend on "repair mechanism"..
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