Two Views Of RNA Polymerase I Structure

Two groups have unraveled a bit more of the mystery of an enzyme that helps transcribe genetic information from DNA to RNA. The researchers have obtained long-sought crystal structures of the eukaryotic enzyme RNA polymerase I (Pol I), a key step toward figuring out how the enzyme works. Eukaryotes have three RNA polymerases—Pol I, II, and III—which transcribe genomic DNA into ribosomal RNA, messenger RNA, and transfer RNA, respectively. Roger D. Kornberg of Stanford University won the 2006 Nobel Prize in Chemistry for determining crystal structures and the mechanism of Pol II. Low-resolution electron microscopy images of Pol I and Pol III had revealed those enzymes’ overall architectures, but their atomic-level structures have been unavailable. Now, atomic-resolution crystal structures of Pol I have been obtained by Carlos Fernández-Tornero of the Spanish National Research Council, Madrid, Christoph W. Müller of the European Molecular Biology Laboratory, Heidelberg, and coworkers and by a team led by Patrick Cramer of the University of Munich (Nature 2013, DOI: 10.1038/nature12636 and 10.1038/nature12712). In a commentary, Joost Zomerdijk of the University of Dundee, in Scotland, says the studies could lead to “a picture of the specific mechanisms and control of ribosomal RNA-gene transcription in eukaryotes.”