DNA Scribes Seen Live

A bank heist is only as fast as the slowest thief, and according to single-molecule studies, genes have a similar limitation. With a fluorescence tracking method, Robert H. Singer at Albert Einstein College of Medicine and colleagues have learned that the rate at which genes are turned on depends on the time it takes for a protein called a transcription factor to hunt down its proper spot on DNA (Science, DOI: 10.1126/science.1202142). Molecular biologists want to learn more about the workings of transcription factor proteins, which bind to DNA to regulate gene expression. Singer’s team engineered nascent RNAs to bind to a molecule of green fluorescent protein, which let them follow transcription in single, live yeast cells with a fluorescence microscope. They learned that the time it took a transcription factor called Mbp1p to find its binding site on DNA dictated gene turn-on rate. The authors say their live-cell technique could unravel the roles of many more players in transcription.