FIGURE 1.

Phosphorylation of TFIIF by CK2. A, RAP74, RAP30 and C-terminal truncations of RAP74 are shown diagrammatically, and the length of each protein is given. Vertical black bars with numbers below the diagram indicate consensus CK2 phosphorylation sites (S/TXXE/D). The numbers give the position of the Ser or Thr residue within that site. Two SD sites, which could also be modified by CK2, are labeled in gray above the diagram and marked by gray bars. Sites labeled with an asterisk were shown to be phosphorylated by HeLa whole cell extract (25). Domain designations are based on Lei et al. (14) and Kamada et al. (51) for RAP74 and Gaiser et al. (52) for RAP30. B, TFIIF containing full-length or truncated RAP74 was phosphorylated by recombinant CK2 in the presence of [γ-³²P]ATP. Proteins were separated by SDS-PAGE. Signal intensity for the gel on the left was adjusted to be darker below the dashed line to reveal labeling of the RAP30 subunit. The positions of the different labeled subunits are indicated on the right.