Rg. Franks et St. Crews, TRANSCRIPTIONAL ACTIVATION DOMAINS OF THE SINGLE-MINDED BHLH PROTEIN ARE REQUIRED FOR CNS MIDLINE CELL-DEVELOPMENT, Mechanisms of development, 45(3), 1994, pp. 269-277
The single-minded gene functions as a master developmental regulator w
ithin the midline cell lineage of the embryonic central nervous system
of Drosophila melanogaster. Genetic experiments suggest that Single-m
inded can function as a transcriptional activator. Regions of the Sing
le-minded protein were fused to the DNA binding domain of the mammalia
n transcription factor Spl and shown to activate transcription from a
reporter gene linked to Spl binding sites. Three independent activatio
n domains were identified in the carboxy terminal region of Single-min
ded that include areas rich in serine, threonine, glutamine and prolin
e residues. Germ line transformation experiments indicate that the car
boxy terminal activation domains, the PAS dimerization domain, and the
putative DNA binding basic domain of Single-minded are required for e
xpression of CNS midline genes in vivo. These results define in vivo a
functional activation domain within Single-minded and suggest a model
in which Single-minded activates transcription through a direct inter
action with promoter elements of CNS midline genes.