Kat - And our final, kind of crazy gene RNA cancer story is about a gene called PTEN and this is a paper published in Nature Structural and Molecular Biology this week from scientists in the US. This is about pseudogenes which sound like kind of fake genes? What's going on here?
Nell - Well, this is interesting because essentially a pseudogene is a bit of DNA thatís almost exactly the same sequence as a gene that's actually doing something, but itís changed slightly. And I guess probably what's happened there is itís got duplicated at some point during evolution. Because youíve got two copies, you donít need both. So, an mutation in one of these copied genes isnít going to cause a problem. So you end up with a slightly mutated gene which becomes a pseudogene. Now obviously, the standard idea would be that this isnít actually doing anything. Itís not coding in the right way for the gene. Itís been mutated so it doesnít matter. Itís just a piece of what we used to call Ďjunk DNAí.
Kat - But weíre not allowed to say that anymore.
Nell - No, weíre not allowed to say that anymore. And thatís because it turns out that it could actually be doing something. So, it's not quite as simple as it first appeared.
Kat - So, what does it looks like itís doing? So, this is a pseudogene for a cancer gene called PTEN which is normally a tumour suppressor.
Nell - Yeah and I mean, the interesting thing here is that because itís so similar to PTEN, itís actually interfering with normal processes involving PTEN inside the cell. So for example, the pseudogene can actually suppress the promoter region for PTEN so essentially, thatís turning it off. And it can also bind, soak up little pieces of microRNA that are meant to be interacting with PTEN. So, itís kind of subverting the normal processes by being such an almost exact copy within the cell.
Kat - I think itís really interesting putting this in the context of what we are now starting to understand about how the levels of gene activity are important. Itís not so much about, ďThis gene is on. This gene is off.Ē Itís actually, ďDo you have an extra dose? Are you making a bit more or a bit less?Ē And gene regulation is getting really complicated because it seems to be maybe about the subtle levels. So, perhaps thatís playing a role here, but thanks very much Nell.