43rd ANNUAL DROSOPHILA RESEARCH CONFERENCE
April 10-14, 2002

PROGRAM AND ABSTRACT VOLUME
Workshop Abstract

16W
Regulating the expression of Actin 57B, the major embryonic myofibrillar actin. Kathleen K. Kelly, Stryder M. Meadows, Richard M. Cripps. University of New Mexico.

To identify regulatory events occurring during myogenesis, we characterized the transcriptional regulation of Drosophila melanogaster Actin 57B, which encodes the major embryonic myofibrillar actin. Act57B transcripts are first detected in visceral muscle precursors and are detectable in all embryonic muscles by the end of embryogenesis. Through deletion analysis we identified a single 595 bp promoter element that was sufficient for high levels of expression in all three muscle lineages. This fragment contained a conserved MEF2 binding site which bound MEF2 protein in embryonic nuclear extracts. Mutation of the MEF2 site severely reduced promoter activity in embryos, and in Mef2 mutants Act57B expression was severely decreased, demonstrating MEF2 is an essential regulator of Act57B. We also showed that MEF2 likely acts synergistically with factors bound to additional sequences within the 595 bp element, and are currently studying additional regulatory events controlling Act57B expression. These findings underline the importance of MEF2 in controlling differentiation in all muscle lineages and also emphasize the requirement of cofactors in MEF2 function.