[Genetic analysis of the interaction of mutations in two genes, controlling expression of MDG4]

Transcription of the retrovirus-like mobile element mdg4 (gypsy) in controlled by the protein product of the suppressor of Hairy wing which interacts with the mdg4 enhancer, and by the protein product of the mdg4 modifier which seems to interact with the su(Hw) protein. In the present work, we studied interaction of mod(mdg4) and su(Hw) mutations in phenotypic expression of mutations induced by mdg4 insertion. Different types of inhibitory effect of mdg4 enhancer on transcription of the target gene were detected. Most frequently, the inhibitory depends on the presence of the mod(mdg4) protein. On of the two acidic domains of su(Hw) protein may be removed without changing the effect. Additional removal of the leucine zipper domain strongly reduces the effect. The second type of inhibition depends of or decrease in the concentration of the mod(mdg4) protein. The su(Hw) protein should have both acidic domains in this case. Sometimes, the su(Hw) protein lacking the C-end acidic domain may activate transcription of a target gene, and this effect does not depend on the presence or absence of the mod(mdg4) protein. The effect may be increased by removal of leucine zipper. Binding of the mod(mdg4) protein to the su(Hw) protein does not depend of the C-end acidic domain and leucine zipper.