Coimmunoprecipitation of Ku with transcription proteins. Immunoprecipitation was performed with anti-RNAP IIo (MAb H5), anti-RNAP IIa (MAb 8WG16), anti-Ku80 (MAb S10B1), anti-DSIF (MAb; Pharmingen), or control (mixture of mouse IgG and IgM, unless otherwise indicated) antibody. Antibodies were cross-linked to agarose beads as described in Materials and Methods. Immunoblots were developed with the ECL enhanced chemiluminescence system (Amersham Pharmacia Biotech) unless otherwise indicated. In all panels, input represents 5 to 10% of material used for immunoprecipitation. (A) HCT116 cell immunoprecipitates probed with antibodies to markers of the elongation complex as indicated. Immunoblots were developed with bromochloroindolyl phosphate and nitroblue tetrazolium (left panel) or with the ECL system (right panel). (B) HCT116 cell immunoprecipitates probed with antibodies to markers of the initiation complex. (C) HeLa cell immunoprecipitates probed with markers to the elongation complex. (D) HeLa cell immunoprecipitates probed with markers to the initiation complex. An asterisk by the CDK9 panel indicates a nonspecific background band.
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