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Friday, August 31, 2012

What Will Some HP Deniers Do With This? P2

I was originally going to title this post "NASA Selects 12 Radiobiology Research Proposals" and announce the news, which I received today.

Thanks for the funding ($12M) NASA!

But then I recalled this video from last year with some of the background information associated with space radiation biology.  Upon revisiting it today, it matched so well with my previous blog post (as well as with the NASA announcement), that I just decided to title this post as Part 2.

If you're a health physics denier of the radiation hormesis strain, you can just pretend the video and the facts described within it don't exist.

The speaker (Dr. P.D. McCormack) discusses DNA double and single strand breaks (DSB's & SSB's) and non-homologous end joining (NHEJ).  The talk is very jargon-heavy and the speaker has a bit of an accent, and you may want to pass on it completely. Alternatively, you can jump to his concluding remarks at 30:50.

But if you're up to the challenge (you can just turn the sound off and read the slides), what follows below is some assistance to understanding what's being said.

The big picture here is that various molecules are recruited by DNA for it's repair as my simple graphic from my previous post depicted.  The speaker describes them in greater detail than is needed for this audience.

He discusses ligation which is related to the fact that there are particular enzymes (ligases) which assist the ends of the DNA strands to join.  The process is called ligation.  He mentions the Ku factors and DNA-PKcs, which are shown in the graphic in my last post.  A heterodimer is a macromolecular complex composed of two different macromolecules.  Endonucleases are enzymes which cleave certain chemical bonds.  Try to not get bogged down in the jargon.

He also briefly touches on homologous repair (HR), which was mentioned in the study within my previous post.  HR looks like this:

If you compare that graphic to the one in my previous post, the major difference here is that an existing DNA strand is used as a template for repair (fifth step from top of graphic).  This makes HR much less error-prone than NHEJ.  Only about 10% of DSB's are addressed by HR, the rest by NHEJ.

Dr. McCormack shows some photos of DSB repair foci (where the repair is happening) and uses a lot of jargon to describe how the cells are stained.  We can ignore that.

The scFv-18 he refers to is a human-manufactured derivative of an antibody (antibodies are large protein molecules that are produced by the immune system), which can bind to DNA-PKcs and inhibit the end joining of DNA via NHEJ.  His point is that we humans might be able to use antibody derivatives or something else to improve NHEJ or shift from NHEJ to HR.

And at the end, he concludes more research is needed.

And as of today, NASA has announced that they have awarded that research.

I'll bet Dr. McCormack will enjoy great intellectual satisfaction in learning of the study I highlighted in my previous post as well as this NASA announcement.

Radiation hormesis propagandists.....not so much.

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