Dual Systems Key to Protect Repetitive DNA

How two different structural apparatuses collaborate to protect repetitive DNA when it is at its most vulnerable – while it is being unzipped for replication, is being discovered by USC scientists.

The centromere—the center of the "X" shape of a chromosome—contains repeated DNA sequences that are epigenetically coded to attract so-called heterochromatin proteins. This protects the structure to ensure that the chromosomes separate properly. If the heterochromatin is lost (due to mutations in the cell), the repetitive DNA becomes vulnerable to rearrangements and recombination. This particularly true during DNA replication, when the DNA is transiently unwound to be copied.

About DNA Fingerprinting
DNA fingerprinting is a technique which helps forensic scientists and legal experts solve crimes, identity thefts, legal suits and terrorism cases.

If there are also defects in replication fork proteins that cause this process to be delayed or inefficient, the rearrangements are dramatically increased. This "genome instability" can lead to loss of genetic information or genetic changes that can lead to cell death or cause cancer.

Susan Forsburg, who led the USC team that conducted the research, used yeast cells to show that simultaneously disrupting both heterochromatin and replication fork proteins caused significant increases in abnormal chromosomes, and in some cases, cell death.

"The insight here is really understanding the mechanism of how these different mutants create a lethal collaboration," said Forburg, a professor of molecular biology at the USC Dornsife College of Letters, Arts and Sciences. "Importantly, all the genes we study have human equivalents—and mutations of some of these are already linked to cancer."

DNA Barcodes to Detect Meat's Variety
With a barcoding procedure based on DNA, scientists from South Africa have made it possible to identify the different varieties of meat.

The research appears online in Cell Reports on March 7. Forsburg worked with Pao-Chen Li, formerly a graduate student at USC and now a post-doctoral researcher at UCSF; as well as Ruben C. Petreaca, Amanda Jensen, Ji-Ping Yuan and Marc D. Green, all from USC.

"We already knew epigenetic modifications change gene expression in cancer," Forsburg said. "Now we see a synergistic effect between the structural role of epigenetic modification that creates heterocrhomatin, and replication fork stability."

Nobel Prize for Discovering the Structure of DNA Up for Auction
For discovering the structure of DNA, the Nobel prize awarded to Francis Crick in 1962 has been put up for auction by his family along with one of his lab coats, his books and other memorabilia.

The next step will be to identify additional components that show this same synergistic effect and to determine what other functions act with heterochromatin to preserve genome stability.

Source-Eurekalert

Algorithm Aims To Make DNA Sequencing Affordable For Clinics
An algorithm that could help make DNA sequencing affordable enough for clinics – and could be useful to researchers of all stripes was developed by two USC scientists.