Structure of an archaeal homolog of the eukaryotic RNA polymerase II RPB4/RPB7 complex

The eukaryotic subunits RPB4 and RPB7 form a heterodimer that reversibly as sociates with the RNA polymerase II core and constitute the only two compon ents of the enzyme for which no structural information is available. We hav e determined the crystal structure of the complex between the Methanococcus jannaschii subunits E and F, the archaeal homologs of RPB7 and RPB4. Subun it E has an elongated two-domain structure and contains two potential RNA b inding motifs, while the smaller F subunit wraps around one side of subunit E, at the interface between the two domains. We propose a model for the in teraction between RPB4/RPB7 and the core RNA polymerase in which the RNA bi nding face of RPB7 is positioned to interact with the nascent RNA transcrip t.