DNA-mediated StyR-P tetramerization. Western blot analysis of StyR-P (100 nM) incubated with increasing amounts of the DNA fragment STY1/STY2 (panel A) or poly d(I)-d(C) (panel B), and afterwards treated with the cross-linking agent DSS. Brackets indicate the 110 kDa band corresponding to StyR-P tetrameric form, and the 75 kDa band derived from incomplete cross-linking of tetramers (see text for details). Dimeric (50 kDa) and monomeric (25 kDa) StyR-P forms are indicated. The concentrations of DNA in each sample were: lane 1, no DNA added; lanes 2 to 5, 50, 100, 200, 400 nM, respectively.