Factors from Trypanosoma cruzi interacting with AP-1 sequences.

Interaction between factors from Trypanosoma cruzi extracts and AP-1 sequences was studied by electrophoretic mobility shift assays. Using a double-stranded probe carrying the AP-1 sequence from the SV40 promoter, three specific complexes designated A, B, and C were detected. Complexes A and C were formed when using single-stranded probes. The relative amount of complex B, specific for double-stranded DNA, increased as a function of probe length. Complexes were stabilized by cross-linking with UVC irradiation and resolved on denaturing SDS-PAGE. Complex A generated bands of 60- and 39 kDa; complex B produced two bands of 46- and 43 kDa; and complex C generated one band of 43 kDa. The AP-1 binding activity was much higher in purified nuclear preparations than in soluble fractions, and was detected in crude extracts from the three forms of the parasite. The binding signal, however, was much stronger in amastigote and trypomastigote than in the epimastigote forms. Specific binding was increased by oxidative stress. Antibodies raised against peptides corresponding to conserved domains of mammalian c-Jun and c-Fos detected bands of 40- and 60 kDa, respectively, in a nuclear epimastigote preparation.