A major discovery about an enzyme's structure has opened a window on understanding DNA repair. Scientists at Duke University Medical Center have determined the structure of a nuclease that will help scientists to understand several DNA repair pathways, a welcome development for cancer research.

Researchers at the University of Pennsylvania School of Medicine are delving into the details of the complex structure at the ends of chromosomes. Recent work, e-published in Nature Structural & Molecular Biology last month, describes how these structures, called telomeres, can be protected by caps made up of specialized proteins and stacks of DNA called G-quadruplexes, or "G4 DNA." Telomere caps are like a knot at the end of each chromosome "string," with the knot's role preventing the string from unraveling.

Thanks to a certain protein, rhesus monkeys are resistant to HIV. Known as TRIM5, the protein prevents the HI virus from multiplying once it has entered the cell. Researchers from the universities of Geneva and Zurich have now discovered the protein's mechanism, as they report in Nature. This also opens up new prospects for fighting HIV in humans.

In the future, when you walk into a doctor's surgery or hospital, you could be asked not just about your allergies and blood group, but also about your gut type. Scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, and collaborators in the international MetaHIT consortium, have found that humans have 3 different gut types. The study, published today in Nature, also uncovers microbial genetic markers that are related to traits like age, gender and body-mass index. These bacterial genes could one day be used to help diagnose and predict outcomes for diseases like colo-rectal cancer, while information about a person's gut type could help inform treatment.