FIG. 1.

N^ic exists in high-molecular-weight nuclear protein complexes with CSL. (A) Schematic representation of N^ic derivatives used in this study. Numbers indicate the N- and C-terminal residues for each construct. The seventh ankyrin repeat is highlighted in silver. All N^ic constructs are engineered with a C-terminal Myc epitope tag (M). (B) Nuclear lysate from a N^ic-transformed RKE cell line was fractionated by size exclusion chromatography. N^ic was visualized by Western blotting with αN^ic-927 (top). Numbers above the lanes indicate collected fractions (I, 10% of total protein input). Arrowheads indicate the native molecular masses of known protein standards: thyroglobulin, 669 kDa; ferritin, 440 kDa; catalase, 232 kDa; and bovine serum albumin, 67 kDa. CSL was detected with anti-CSL antisera. (C) N^ic and CSL are physically associated in the high-molecular-weight complex. Three fractions encompassing the indicated gel filtration peaks were pooled and immunoprecipitated with an αN^ic-927. Immunoprecipitates were detected with the indicated antibody.