Detection of c-Fos immunoreactive species. A) Nucleotide sequence of c-fos intron 3 and flanking exons 3 and 4. Lower case letters refer to intronic nucleotides and upper case letters to exonic nucleotides. Minimal functional sequences within the mCRD are underlined. The encircled triplets encode the aa residues that contact to DNA. Triplets encoding two out of the five-leucine residues of the LZ motif are indicated in italics. The stop codon in intron 3 is boxed and shaded in grey. B) Western blot analysis of c-Fos proteins purified by immunoaffinity chromatography. A crude extract from NIH 3T3 cells stimulated with serum for 30 min was loaded onto the immunoaffinity column. The column eluate (E-30), as well as the input crude extract (CE-30) and the crude extract from serum-starved (CE-0) cells were subjected to inmunoblot analysis as described under "Methods". The positions of molecular size standards are indicated on the left in kDa. GAPDH was used for loading control.