A group of researchers at the University of Pittsburgh say they have made a breakthrough in understanding how damaged DNA is repaired. PhD. Bennett Van Houten is with the University of Pittsburgh Cancer Institute and the lead author of the paper published in today’s issue of Molecular Cell. Van Houten says they attached “quantum dots” to DNA-Repair proteins in an effort to watch them work. The dots shine brightly when exposed to light and this allowed the researchers to track their movement along strands of DNA that had been unraveled and stretched around a bead. In a normal cell the proteins search out damaged sections of DNA and then call in other proteins to make repairs. Van Houten says they went into the research wondering how the relatively small numbers of these special protein molecules were able to check so much DNA. Some theorized that the proteins would make random hops around the DNA strand while others believed the protein would slide up and down the DNA. Critics of the jumping theory said it was too inefficient but critics of sliding noted that DNA in a cell is crumpled up into a ball and the slider’s path would be blocked from time to time. Van Houten says what they found was that both methods are used. The proteins slide down the DNA for about seven seconds and then hop to another area of the strand. With the DNA on the surface of a bead and the quantum dots attached Van Houten and his team were able to get video of the movement.
All cells have these proteins and if they stop working the cells cannot survive. Van Houten says, “Everyone is constantly bombarded with environmental toxins that inflict small errors in the DNA code, so a rapid repair system is essential to maintain the integrity of the sequences for proper cell function.” Now that they have a better understanding of the movement of these repair proteins, Van Houten says scientists can start to use the knowledge to begin new efforts to prevent cancer and make cancer drugs more effective.