Quadruplex DNA

07 February 2013

Interview with

Nell Barrie

Nell - Well, the first thing we've picked out is a really interesting story about quadruplex DNA which sounds like this big new, exciting thing, but in actual fact, not quite as new and exciting as some of the reports made out.

Kat - It was like, "Oh my God! It's the new DNA helix. Everything we know is wrong." It's not.

Nell - DNA 2.0.

Kat - People have known about this for quite a long time and in fact, this isn't actually the first time they found quadruplex DNA in humans because they did that in 2011, the same group. But what is quadruplex DNA?

Nell - So, this is a type of DNA, so that instead of being two halves curled into a nice little spiral - how everyone sees it in cool little 'sciency' bits of films and on TV.

Kat - The double helix.

Nell - Exactly. It's curved around. It's almost like a circle, so it's got four sides to it. So, it's kind of a square-ish circle sort of formation and it's to do with what that particular section of DNA is actually made up of. So, if it has a lot of guanine in it, it could be that that's what makes it curl up into this particular shape.

Kat - So, it's the physical properties of the chemicals that are making up that stretch of DNA and it turns out, there's a lot of these guanine, or G-rich, sequences in telomeres at the ends of our chromosomes. And funnily enough, that's obviously where they found them and they've done a really nice technique. This is a research from Shankar Balasubramanian and Giulia Biffi. Tell me a bit about what they actually did to spy on this DNA in cells.

Nell - So, you mentioned that we have already seen evidence that human cells can have this kind of quadruplex DNA and we already knew that some other forms of life - so small organisms, single-celled organisms - might have it. But now, we know it's in human cells too. We did already have evidence of this, but what the new research has done is actually looked at when the quadruplex DNA is produced. So, which stage of the cell cycle, when it appears, when it disappears, and they've been able to tag it with a fluorescent marker so they can essentially watch it appearing, disappearing, moving around.

Kat - And when is it mostly turning up?

Nell - So, it's in a phase called S-phase. 'S' stands for synthesis and essentially, what's happening then is all the DNA in a cell is being copied. And this is quite interesting because in terms of relevance to cancer, it's a stage when a lot of cancer drugs will act on the cell and they'll stop various things from happening in the cell at that point in time.

Kat - So, that's also quite a good opportunity to intervene as well if you wanted to maybe get drugs that stuck to the quadruplex DNA or interfered with it in some way. That would be pretty good.

Nell - Exactly, so the idea here is that if it turns out that quadruplex DNA is playing a role in driving cancer cells, making them grow, making them divide, it could be a chance for people to develop drugs that perhaps latch onto the quadruplex DNA, block it from doing whatever it's up to in the cell, and that could be a new way to tackle cancer cells.

Kat - Or even if it's not driving them, if it's just there, if it's maybe some kind of marker that happens to be there more in cancer cells - we don't really know. It's very interesting. That came out in Nature Chemistry this week from the team at the University of Cambridge.

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