FIG. 1.

Schematic diagrams of Chk2 and Chk2 mutants. SCD, FHA, and kinase catalytic domains are marked, with amino acid coordinates above. CΔ1 corresponds to a spontaneous variant of CHK2 from Li-Fraumeni syndrome, with a frameshift mutation causing readthrough into alternate reading frames as indicated. CΔ2, a similar frameshift mutation thought to be a spontaneous variant of CHK2 from Li-Fraumeni syndrome, was found to be a polymorphism in the homologous fragment present on chromosome 15 (53). KD is kinase defective owing to substitutions of conserved residues in the catalytic domain. R117A and NGT/AAA are substitutions of conserved FHA domain residues. 7A has alanine substituted for each S or T of all seven SQ and TQ sites within the SCD. 2FKBP contains two copies of the FKBP mutant (F36V) fused to the amino terminus of Chk2.