FIG. 1.

Specificity of mAb 7C2. About 1 μg of DE1.0, a 1 M KCl eluate from a DEAE-5PW chromatography corresponding to a partially purified RNA polymerase II fraction from HeLa cells [see (25)], was loaded on a 5% polyacrylamide SDS gel (29). After electrophoresis, the proteins were transferred to a nitrocellulose membrane and incubated with the mAb 7C2. Specific immune complexes were revealed by the ECL Western blotting detection system (Amersham International pic, Buckinghamshire, UK), as previously described (8). The positions of the phosphorylated (Ho) and unphosphorylated (11a) largest subunit of RNA polymerase II are indicated.