Figure 1.

Unique cysteines in the POU_S and POU_H domains effective for protein–DNA crosslinking. (A) Representation (adapted from refs. 2 and 4) of the Oct-1 POU domain–octamer site crystal structure with the positions of the unique cysteines used for crosslinking analysis indicated (UC54 in the POU_S domain and UC7 in the POU_H domain; the precise location of UC54 is hidden behind helix 2 on the turn between helices 3 and 4). (B) SDS/PAGE analysis of crosslinked protein–DNA complexes after UV irradiation of POU domain-binding reactions containing no protein (lanes 1, 4, 7, and 10), POU_S-UC54 protein (lanes 2, 5, 8, and 11), or POU_H-UC7 protein (lanes 3, 6, 9, and 12). Shown are crosslinked complexes formed on the upper and lower strands of the histone H2B octamer and the (OCTA⁻)TAATGARAT sites, as indicated.