In Science this week, a team of UK scientists report the discovery of multiple proteins responsible for the disassembly of the replisome, the structure responsible for synthesizing complementary DNA strands during chromosome replication. They showed that a ubiquitin ligase promotes ubiquitylation of CMG, the ring-shaped DNA helicase that unwinds DNA at the start of replication. Another protein complex then associates with the ubiquitylated CMG, leading rapidly to helicase disassembly.
Meanwhile, in Science Translational Medicine, researchers from Johns Hopkins University School of Medicine describe a new molecular imaging technique that can detect infection by drug-resistant bacteria. The method involves a probe made of a radioisotope tagged with a sugar molecule called sorbitol that is exclusively taken up by the Enterobacteriaceae, a family of Gram-negative bacteria that normally inhabit the gastrointestinal tract, but are the most common cause of Gram-negative bacterial infections in humans. When combined with positron emission tomography imaging, the signal from the probe revealed the presence of bacteria in the bodies of mice, and could distinguish between infection and general inflammation, as well as between Gram-negative and Gram-positive infection. If translated into humans, the approach could be used to rapidly identify whole-body infection and drug resistance.