Monday, December 28, 2009

A Cellular Response to Broken Chromosomes

Science Daily features an article titled How Cells Handle Broken Chromosomes. Quoting from the article:

Scientists have discovered a novel cellular response towards persistent DNA damage: After being recognized and initially processed by the cellular machinery, the broken chromosome is extensively scanned for homology and the break itself is later tethered to the nuclear envelope. The researchers have uncovered a surprising feature of how DNA strand breaks can be handled.

The writer notes elaborate DNA repair systems involved in the repair of DNA double strand breaks (DSB). Researchers observed a "tethering" of yeast DSB to the nuclear envelope. It was speculated that this might prevent errors engendered by recombination. Rad51, sometimes dubbed recombinase, spreads over the chromosome containing the break during the repair process. Another protein, H2A.Z, is also essential for the activation of Rad51 and relocating DSBs to the nuclear envelope. When H2A.Z is not present in cells such cells are very sensitive to DSBs.