Researchers unravel protein role in repair of cancer damaged cell

Washington, Jan 7 : A key protein in cells plays a critical role in not one but dual processes affecting the development of cancer, according to a new discovery.

"Most proteins involved in responding to DNA damage that can cause cancer either help detect the damage and warn the rest of the cell, or help repair the damage," said David O. Ferguson, the study's co-author.

Previous research has shown that the protein, Mre11, functioned as a "gatekeeper" to signal injury to the cell and prevent damaged cells from proliferating.

Now, Ferguson, assistant professor of pathology at the University of Michigan Medical School, and colleagues have discovered that in mammals a function of the Mre11 protein also serves as a "caretaker," by repairing DNA.

Their findings could have important implications for cancer treatment by permitting oncologists to predict a tumour's sensitivity to radiation and other therapies, making it more vulnerable to treatment.

Under normal circumstances, the body's cells grow, divide and eventually die. When something damages a healthy cell's DNA - such as radiation or exposure to a toxin - a multiprotein complex steps in to repair the breakage and activate other fundamental cellular processes.

The MRN complex, comprising Mre11, Rad50 and NBS1 proteins, senses DNA damage, known as double-strand breaks, within the cell. The complex then transmits that information to an enzyme called the ATM (ataxia-telangiectasia mutated) checkpoint kinase, said a Michigan release.

The ATM kinase controls the cell's response to double-strand breaks, and slows cell growth to give the cell opportunities to repair them, says Ferguson.

What Ferguson and colleagues discovered is that Mre11 not only senses and communicates damage, it also repairs DNA double-strand breaks by acting as a nuclease, an enzyme that modifies and processes the broken DNA ends.

The study was published in the journal Cell.

--IANS