Professor Joan Steitz - Viral RNAs

Kat - Joan Steitz at Yale University has worked on RNA for more than three decades, and specialises in the small RNAs produced by viruses. I started by asking her how RNA research has grown in importance over recent years.

Joan - Our cells, I think the latest numbers were something like 2,000 of these microRNAs are known to be made by our cells in various tissues at various stages of development. And they have huge impact on the actual output of the genes in terms of the protein - huge expansion in terms of the appreciation of RNA, and its regulatory roles in the whole process of DNA makes RNA makes protein.

Kat - So, we've got the messenger RNAs that tells cells what proteins to make, we've got all these microRNAs controlling things, we've got tRNAs that help to build proteins, and all the RNAs that are part of the machinery of cells. What's your favourite one? What's the one that you're working on?

Joan - I don't know that I have favourite ones, but I do like the RNAs that are in the so-called 'snurps' (snRNPs) that are part of the splicing apparatus, because we worked on those for a very long time. At the moment, we're working on viruses and it turns out that many of the viruses that infect us also make non-coding RNAs in order to manipulate the cells that they live in and help them with their lifecycles. And the really fun thing about viruses is that viruses don't really sort of make things up. They get things from their host and then they adapt them to the ends of the virus. And so, viruses can make non-coding RNAs that you look at it and you say, "Oh, I know what that RNA does" because you know what the host RNA that looks like that does. But it turns out that viruses are very clever and in many cases, they've completely changed with that RNA might do into doing something completely different that fits with what the virus needs it to do. So, that's providing lots of insights into the evolution and how some of these control mechanisms came to be and how versatile they are.

Kat - You mentioned evolution and I know that it's usually thought that RNA evolved before DNA and the fact that we're discovering so much more about these RNAs and what they do, and that they're involved in viruses, are we almost getting a window on what our previous biological world was like?

Joan - I think you're absolutely right, yeah. I don't believe in a pure RNA world. This is just personal. I think that RNA has always existed with helper peptides or proteins that bound to them, and made them more functional for the various functions that they're carrying out. But I think we are getting, especially now with massive databases and being able to compare and contrast what one sees in one organism or another versus what one sees in a particular virus or another that we're getting a whole new view into the possible ways that things could've evolved.

Kat - That was Professor Joan Steitz, from Yale University.