Posttranscriptional regulation of Apterous activity during wing development. U. Weihe , M. Milan , S.M. Cohen. Developmental Biology Program, EMBL, Heidelberg, Germany.

   The selector gene apterous encodes a LIM-homeobox transcription factor which regulates dorso-ventral axis formation in the Drosophila wing. Apterous protein is specifically expressed in the dorsal compartment and activates several target genes, including Serrate and fringe involved in signaling across the DV boundary. Apterous activity depends on its ubiquitous cofactor dLDB/Chip. Apterous activity is antagonized by the LIM-only protein dLMO. We will present evidence that dLMO protein reduces Apterous protein levels post-transcriptionally. dLMO appears to work by preventing Apterous from forming stable DNA binding complexes with dLDB/Chip. This suggests that disturbing the interaction between Chip and Apterous leads to the degradation of Apterous. We are testing the possibility that a difference in affinity between dLMO and Apterous for CHIP might explain the observation that overexpression of Apterous in its own domain does not increase Apterous activity in vivo.