Scientists discover cellular 'SOS' signal in response to UV skin damage

Mar 15, 2007

New research from the University of North Carolina at Chapel Hill School of Medicine has identified two proteins that may help protect against skin cancer.

The study, which appears in the advance online edition of the journal Molecular and Cellular Biology, indicates that two proteins, named Timeless and Tipin, form a complex that regulates the rate at which DNA is replicated after exposure to ultraviolet radiation.

Ultraviolet radiation in sunlight damages the DNA in skin cells. If left unrepaired by the cell, this damage can turn into mutations that lead to cancer. Before cells divide, they must replicate, or copy, their DNA to form new daughter cells. If damage in the DNA is discovered even after the cell has given a "go-ahead" to replicate its DNA, the Timeless/Tipin complex sends a signal throughout the nucleus of the cell to slow the rate of replication. This slowdown may give the cell additional time to repair its DNA and potentially save itself from becoming cancerous or from dying in response to ultraviolet radiation.

"What we discovered here was that the cell can send out an additional SOS and slow DNA replication even after it has begun," said Dr. William Kaufmann, a professor of pathology and laboratory medicine and a member of the UNC Lineberger Comprehensive Cancer Center and Center for Environmental Health and Susceptibility.

"We've known for 25 years that a cell can stop DNA replication from even starting when it detects damage in its own DNA – this gives the DNA repair mechanisms in the cell the time to find and repair the damage," he said.

Using an innovative new technique to visualize the replication of DNA strands exposed to ultraviolet radiation, Kaufmann and his co-authors noted a slowdown in DNA replication when Timeless and Tipin were present in the cell. Building blocks for DNA were labeled with fluorescent molecules so that tracks of newly synthesized DNA could be observed under the microscope and their lengths measured.

Though the study specifically examined only the Timless/Tipin response to ultraviolet radiation, Kaufmann speculates that this response may be relevant to other types of DNA damage as well – including those used as treatments for cancer.

"This protective response may make some cells more resistant to certain types of cancer therapies which work by inducing the cancer cell to die. If the cell, even if it is a cancer cell, is given this additional time to recover from treatment, it may be able to survive it, much to the detriment of the patient." Kaufmann said.

Ultraviolet radiation in sunlight causes at least one million cases of skin cancer in the U.S. annually and greater than fifty thousand cases of melanoma.

Source: University of North Carolina School of Medicine

Explore further: Blood and saliva tests help predict return of HPV-linked oral cancers

add to favorites email to friend print save as pdf

Related Stories

Sapphire talk enlivens guesswork over iPhone 6

7 hours ago

Sapphire screens for the next iPhone? Sapphire is second only to diamond in hardness scratch-proof properties, used in making LEDs, missiles sensors, and on screens for luxury-tier phones. Last year, the ...

The source of the sky's X-ray glow

10 hours ago

In findings that help astrophysicists understand our corner of the galaxy, an international research team has shown that the soft X-ray glow blanketing the sky comes from both inside and outside the solar system.

Recommended for you

New paper describes how DNA avoids damage from UV light

11 hours ago

In the same week that the U.S. surgeon general issued a 101-page report about the dangers of skin cancer, researchers at Montana State University published a paper breaking new ground on how DNA – the genetic code in every ...

Drug target identified for common childhood blood cancer

12 hours ago

In what is believed to be the largest genetic analysis of what triggers and propels progression of tumor growth in a common childhood blood cancer, researchers at NYU Langone Medical Center report that they have identified ...

User comments : 0