Structural Basis of Transcription: RNA Polymerase II at 2.8 Ångstrom Resolution
Patrick Cramer,*
David A. Bushnell,
Roger D. Kornberg
Structures of a 10-subunit yeast RNA polymerase II have been
derived from two crystal forms at 2.8 and 3.1 angstrom resolution. Comparison of the structures reveals a division of the polymerase into
four mobile modules, including a clamp, shown previously to swing over
the active center. In the 2.8 angstrom structure, the clamp is in an
open state, allowing entry of straight promoter DNA for the initiation
of transcription. Three loops extending from the clamp may play roles
in RNA unwinding and DNA rewinding during transcription. A 2.8 angstrom
difference Fourier map reveals two metal ions at the active site, one
persistently bound and the other possibly exchangeable during RNA
synthesis. The results also provide evidence for RNA exit in the
vicinity of the carboxyl-terminal repeat domain, coupling synthesis to
RNA processing by enzymes bound to this domain.
Department of Structural Biology, Stanford University School of
Medicine, Stanford, CA 94305-5126, USA.
*
Present address: Institute of Biochemistry, Gene Center,
University of Munich, 81377 Munich, Germany.
To whom correspondence should be addressed. E-mail:
kornberg{at}stanford.edu
