Transcriptional regulation of the Drosophila melanogaster muscle myosin heavy-chain gene

Abstract

We show that a 2.6 kb fragment of the muscle myosin heavy-chain gene (Mhc) of Drosophila melanogaster (containing 458 base pairs of upstream sequence, the first exon, the first intron and the beginning of the second exon) drives expression in all muscles. Comparison of the minimal promoter to Mhc genes of ten Drosophila species identified putative regulatory elements in the upstream region and in the first intron. The first intron is required for expression in four small cells of the tergal depressor of the trochanter (jump) muscle and in the indirect flight muscle. The 3′ end of this intron is important for Mhc transcription in embryonic body wall muscle and contains AT-rich elements that are protected from DNase I digestion by nuclear proteins of Drosophila embryos. Sequences responsible for expression in embryonic, adult body wall and adult head muscles are present both within and outside the intron. Elements important for expression in leg muscles and in the large cells of the jump muscle flank the intron. We conclude that multiple transcriptional regulatory elements are responsible for Mhc expression in specific sets of Drosophila muscles. KeywordsDrosophila melanogaster; muscle; myosin heavy chain; transcription; enhancer; gene regulation Drosophila melanogaster is unusual in having a single muscle myosin heavy-chain gene (Mhc) (Bernstein et al., 1983;Rozek and Davidson, 1983), rather than a Mhc multigene family (see Emerson and Bernstein, 1987 for review). Alternative splicing of the primary transcripts from this gene yields multiple isoforms of the protein (Collier et al., 1990;George et al., 1989;Hastings and Emerson, 1991;Kazzaz and Rozek, 1989;Kronert et al., 1991;Zhang and Bernstein, 2001). Drosophila Mhc is expressed in all muscles at embryonic, larval, pupal and adult stages. Thus several stage-or muscle-specific enhancer elements may regulate its transcription.Transcriptional regulatory regions for a number of Drosophila muscle genes have been mapped, resulting in the identification of both unique and shared cis-acting elements (Arredondo et al., 2001;Kelly et al., 2002;Marin et al., 2004;Mas et al., 2004;Meredith and Storti, 1993). The latter includes E-boxes that bind helix-loop-helix transcription factors and MEF2 sites that bind MEF2 protein (Bour et al., 1995; Lilly et al., 1995). E-boxes, MEF2 sites and their binding factors positively regulate vertebrate muscle gene expression as well (see Molkentin and Olson, 1996 for review).* Corresponding author. Tel.: +1-619-594-5629; fax: +1-619-594-5676; E-mail address: sbernst@sunstroke.sdsu.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal dis...

Myocyte Enhancer Factor 2 and Chorion Factor 2 Collaborate in Activation of the Myogenic Program in Drosophila

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“…The Mhc reporter construct, pMHC-LacZ1, harboring the genomic sequence from positions Ϫ2759 to ϩ 2124 of the Myosin heavy chain gene was kindly provided by S. I. Bernstein (San Diego State University, San Diego, CA) (21).…”

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