A DROSOPHILA PROTEIN RELATED TO THE HUMAN ZINC-FINGER TRANSCRIPTION FACTOR PRDII MBPI/HIV-EP1 IS REQUIRED FOR DPP SIGNALING/

Little is known about the signal transduction pathways by which cells respond to mammalian TGF-beta s or to decapentaplegic (dpp) a Drosophi la TGF-beta-related factor, Here we describe the genetic and molecular characterization of Drosophila schnurri (shn), a putative transcripti on factor implicated in dpp signaling. The shn protein has eight zinc fingers and is related to a human transcription factor, PRDII/MBPI/HIV -EP1, that binds to nuclear factor-kappa B-binding sites and activates transcription from the HIV long terminal repeat (LTR), shn mRNA is ex pressed in a dynamic pattern in the embryo that includes most of the k nown target tissues of dpp, including the dorsal blastoderm, the mesod ermal germlayer and parasegments 4 and 7 of the midgut, Mutations in s hn affect several developmental processes regulated by dpp including i nduction of visceral mesoderm cell fate, dorsal/ventral patterning of the lateral ectoderm and wing vein formation, Absence of shn function blocks the expanded expression of the homeodomain protein bagpipe in t he embryonic mesoderm caused by ectopic dpp expression, illustrating a requirement for shn function downstream of dpp action. We conclude th at shn function is critical for cells to respond properly to dpp and p ropose that shn protein is the first identified downstream component o f the signal transduction pathway used by dpp and its receptors.