Chromosome's Guardians Susceptible to UV Radiation, Scientists Find

April 30, 2010
A chromosome with DNA

(PhysOrg.com) -- The molecular caps at the ends of chromosomes that protect humans against cancer and premature cellular aging show a surprising inability to protect themselves against ultraviolet radiation, a new Yale School of Medicine study has found.

Telomeres—the repeat sequences of DNA at the end of chromosomes that act like plastic tips at the end of a shoelace—are much more likely to be damaged by than are other common cellular structures, researchers report in the study published online April 29 in the journal .

“This damage is not repaired. It is as if the cell has decided to defer maintenance to the ,” said Douglas Brash, professor of therapeutic radiology, genetics and dermatology, a researcher for the Yale Cancer Center, and senior author of the study.

As cells divide over a lifetime, telomeres tend to wear down, and the resulting instability of can lead to problems such as increased risk of cancer. As telomeres shorten, cells begin to age, deteriorate and eventually die.

Given their importance, scientists expected telomeres to possess robust defense mechanisms. Brash and Yale postdoctoral researcher Patrick Rochette, now assistant professor at Laval University, Quebec, tested the hypothesis by bombarding human cells with . They found 10 times more DNA damage in telomeres than to the p53 gene, to a gene encoding a subunit of the cell’s ribosome or to . And the damage to the telomeres was not repaired.

“There may be many reasons for this, but it looks like the medicine might be worse than the disease,” Brash said.

An overly robust response to fix damage at the tips of the chromosome might trigger even bigger problems for the cell - such as causing breaks within double strands of DNA, Brash speculated.

The strategy, however, is not without risk. Over many years, the accumulating damage may make the telomeres harder to copy when the cell divides, eventually leading to cell aging and death.

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6 comments

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SDrapak
not rated yet Apr 30, 2010
Cell death might be the best thing for a cell that's been bombarded with UV and possibily damaged in many other ways
Skeptic_Heretic
not rated yet Apr 30, 2010
Cell death might be the best thing for a cell that's been bombarded with UV and possibily damaged in many other ways

Problem is the telomeres being damaged is also thought to be one of the causes of cancer. UV bombardment of the telomeres, and the resulting damage, is most probably the cause for cancers like skin melanoma.
Megadeth312
not rated yet Apr 30, 2010
I guess longevity wasn't an evolutionary factor for humans, you'd think there would be a repair mechanism for Telomeres.
mattytheory
not rated yet Apr 30, 2010
I guess longevity wasn't an evolutionary factor for humans, you'd think there would be a repair mechanism for Telomeres.


What are you talking about? Humans on average live longer than most other animal species on the planet.
Skeptic_Heretic
not rated yet Apr 30, 2010
I guess longevity wasn't an evolutionary factor for humans, you'd think there would be a repair mechanism for Telomeres.


What are you talking about? Humans on average live longer than most other animal species on the planet.


Not really. We're about dead set in the middle if you remove insects from the equation.
maxcypher
not rated yet Apr 30, 2010
We need to create an artificial repair mechanism for Telomeres.

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