Protein May Make UV Exposure Safer In Morning

From Scientific American

Levels of a DNA repair protein naturally rise in the morning and fall later in the day, which may make exposure to UV safest early.

The early bird gets the worm—and may avoid skin cancer. Because a new mouse study suggests that, for humans, tanning in the mornings may be less likely to permanently damage DNA and cause skin cancer.

A mouse’s levels of the DNA-repairing protein XPA are different from ours—they peak in the morning and bottom out in the evening. Researchers exposed mice to UV radiation when their XPA was at its minimum level, around 4 a.m., and others to the same rays around 4 p.m., when XPA levels peaked.

Mice who tanned while low on the repair protein developed skin cancer faster and five times more frequently than their evening-tanning counterparts. The study is in the Proceedings of the National Academy of Sciences. [Shobhan Gaddameedhi et al, Control of skin cancer by the circadian rhythm]

Unlike mice, humans are not nocturnal, so their XPA levels rise and fall at different times. In people, XPA is at prime DNA-repairing levels in the morning, which thus looks the safest time for UV exposure. So if you want to avoid skin cancer, probably go to the tanning salon early—or better yet, don’t go at all.

  1. #1 by Lishuang Chen on November 25, 2011 - 5:09 am

    Thanks Ian for tirelessly feeding us these interesting articles. I enjoyed them all !

  2. #2 by Hein Vandenbergh on November 26, 2011 - 5:16 am

    “Go to the tanning salon early” Hey wot?! Who ARE these people……..

    Then again, at long last someone mentions the DNA repair protein, about which I have been harping-on on the blog since the early days, without anyone ever acknowledging it. I first heard about it ‘from the horse’s mouth’, its discoverers’, at the World Skin Cancer Congress in Zurich in July 2001.

    I was beginning to think I must have misheard it at the time [Scott Menzies and Margaret Stewart were sitting either side of me – I was going to ask them next time I saw either], as there was simply never any reaction to it – like so much on the blog. Unless it’s Harald or another ‘name’….. or a blood vessel-type: ad infinitum, even though in real life most of that fine detail you do not see, or cannot see. I’m either too busy or not anal enough 🙂

    Thanks Ian – I won’t have that brain scan now.

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