16. Seeing Behind the Gene Transcription Scene
(l.) John Lis (r.) Watt Webb
John T. Lis, Molecular Biology and Genetics, Watt W. Webb, Applied and Engineering Physics, and research colleagues revealed that the molecular machinery behind gene transcription is not stationed in special transcription factories within a cell nucleus. Instead, the enzyme RNA polymerase II (Pol II) and other key molecules can assemble at the site of an activated gene, regardless of the gene’s position. They observed polytene chromosomes—large, multistranded chromosomes in the salivary gland tissue of fruit flies that have hundreds of sets of the genome, instead of the usual two sets in conventional cells—using multiphoton microscopy developed by Webb, which allows high-precision 3-D imaging in living cells. The researchers activated heat shock genes, which protect cells from sudden rises in temperature, and watched them in real time as they began to be transcribed. They tagged Pol II with a fluorescent marker to track its movements within the nucleus. The research will lead to developing new ways of actually seeing, in vivo, how gene regulation works.