This group has continued its study of three sequence-specific DNA-binding proteins in Drosophila, the heat shock transcription factor HSF, and two factors which regulate the segmentation gene fushi tarazu, FTZ-F1 and tramtrack. With the cloning of the HSF gene from human in the previous year, a comparative study of HSF function in human and Drosophila is under way. Considerable progress has been made in the molecular genetic analysis of the regions of the HSF protein that are important for its regulation. The most interesting result regarding HSF regulation has been the demonstration of the importance of the C-terminal leucine zipper motif in maintaining the inactive HSF conformation. Another significant achievement was the successful demonstration of the proposed function of the tramtrack protein as a repressor of the ftz gene. An additional highlight came from the immunostaining analysis of FTZ-F1 on Drosophila polytene chromosomes which revealed a new function for FTZ-F1 as an intermediate regulator of genes expressed at the onset of metamorphosis. These findings further affirm the phenomenon of regulatory pleiotropy, and suggest that many transcription factors regulating developmental genes are utilized repeatedly throughout the life of the organism to serve different regulatory pathways.
