Image analyses of native bovine RNAPII complexes. (A) Native bovine RNAPII(G),
enriched in monomers (white circles), were preserved in negative stain (2% uranyl
acetate, 50 nm bar scale). (B) Upper row: class averages of bovine
RNAPII(G) particles obtained after reference-free alignment and clustering reveal
renowned RNAPII features such as groove and stalk (Rpb4/7). Lower row: re-projections
from the 3D reconstruction of native RNAPII(G) that best match the class averages above.
(C) EM structure of the native bovine RNAPII(G) superimposed with the yeast
RNAPII X-ray structure (PDB: 1WCM). (D) Native bovine RNAPII, enriched in dimers
(white circles), preserved in negative stain (50 nm scale bar scale). (E)
A representative class average of RNAPII dimer. (F) 3D model of the RNAPII dimer
built from reconstruction RNAPII monomers. An orientation best matches the class average
in (E) shows subunit Rpb3 and Rpb4 likely participate the dimer interface.