Fig. 5. Tau protein associates with -satellite DNA. The association of tau protein with -satellite DNA was analyzed by electrophoretic mobility shift assay (EMSA). (A) Purified tau protein from bovine brain was resolved by 12% SDS-PAGE and then stained with Coomassie Blue (CB) or immunodetected with Tau-5 monoclonal antibody to confirm the absence of contaminants. (B) Different concentrations of purified tau protein (100 ng, 200 ng, 300 ng and 400 ng) were incubated with the ³²P-labeled -satellite DNA probe of 700 bp. The incubations were performed in the presence of 0.5 µg unlabeled sonicated salmon sperm DNA (ssDNA) used as random non-sequence specific competitor DNA in 50 mM NaCl buffer. The EMSA gels were dried and radioactivity was visualized using PhosphorImager and the computer program ImageQuant. The arrows indicate the shift observed for the labeled probe owing to the interaction of the probe with tau and the free probe.