by Rathi Manohar on  June 25, 2010 at 8:10 PM Cancer News
Genetic Disorder - How It Causes Skin Cancers
People with an inherited genetic disorder - xeroderma pigmentosum (XPV)which makes them very sensitive to sunlight, have an enzyme missing and this makes them more prone to get skin cancers.

The findings by researchers from Mount Sinai School of Medicine, paves way towards therapies that would help protect people with XPV from developing skin cancers.

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The research team determined that, in the general population, DNA polymerase eta, an enzyme able to overcome the barriers created by sun damage and ultraviolet rays and continue replicating DNA strands, is structured differently from any other polymerase.

However, in people with XPV, since this enzyme is missing, they fail to bypass this damage, causing the replication process to stall, resulting in mutations and extremely high susceptibility to skin cancer.

Researchers have never been able to fully determine a structural basis for why the enzyme can get around UV damage.

After nearly a decade of research, the researchers successfully developed a crystal model, or a three dimensional chemical derivation, of the enzyme.

They determined that in the general population, DNA polymerase eta suppresses skin cancer because the active site, where chemical reactions required to replicate DNA take place, can adjust much better to UV damage than any other DNA polymerase.

"We have been unable to study how DNA polymerase eta can replicate through UV damage because we did not have a crystal structure of the enzyme to study. Our team succeeded in developing this structure and determining what makes this enzyme unique," Nature quoted Dr. Aneel K. Aggarwal, Professor, Structural and Chemical Biology, Mount Sinai School of Medicine, as saying.

The researchers generated crystals and analyzed them using X-rays.

They determined that the active site of DNA polymerase eta is structured in such a way that it can easily accommodate the UV induced DNA lesions and replicate through them.

"Now that we know the structural basis for the suppression of skin cancers by this enzyme, one question for the future is if there's a way to restore its function in people with XPV and reduce their risk for cancer," said Aggarwal.

The study is published in the current issue of the journal Nature.

Source: ANI

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