Novel Mechanism for DNA Repair

A new mechanism has been proposed for the repair of damaged DNA by mobile bits of DNA called long interspersed elements, or LINE-1s (L1s). These make up about 17% of human DNA, but little is known about their role in cell metabolism.

A study published in the June 2002 issue of Nature Genetics provides new insights into the role of L1s in the repair of broken strands of DNA. This work is the result of a collaboration between researchers from the University of Michigan Medical School (Ann Arbor, USA) and Louisiana State University (Baton Rouge, USA).

It was previously known that L1s utilize reverse transcriptase to replicate themselves and an endonuclease to cut the genetic DNA and create a space, so they can insert themselves into the genome. "We knew about the endonuclease pathway,” says Tammy A. Morrish, first author of the paper. "But we did not know there was another mechanism that did not require endonuclease, or that L1s could jump into existing breaks in DNA.”

The current study describes a pathway for L1 retrotransposition in Chinese hamster ovary cells that acts independently of endonuclease but is dependent on reverse transcriptase. These findings suggest that L1s can integrate into lesions, resulting in retrotransposition-mediated DNA repair.

Future studies will examine whether it is possible to direct L1s to repair specific breaks in DNA, whether L1s can be used as vectors to deliver genetic material to specific DNA locations, and the impact of an L1 insertion on genes.




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