Sequence requirements for myosin gene expression and regulation in Caenorhabditis elegans.
Four Caenorhabditis elegans genes encode muscle-type specific myosin heavy chain isoforms: myo-1 and myo-2 are expressed in the pharyngeal muscles; unc-54 and myo-3 are expressed in body wall muscles. We have used transformation-rescue and lacZ fusion assays to determine sequence requirements for regulated myosin gene expression during development. Multiple tissue-specific activation elements are present for all four genes. For each of the four genes, sequences upstream of the coding region are tissue-specific promoters, as shown by their ability to drive expression of a reporter gene (lacZ) in the appropriate muscle type. Each gene contains at least one additional tissue-specific regulatory element, as defined by the ability to enhance expression of a heterologous promoter in the appropriate muscle type. In rescue experiments with unc-54, two further requirements apparently independent of tissue specificity were found: sequences within the 3' non-coding region are essential for activity while an intron near the 5' end augments expression levels. The general intron stimulation is apparently independent of intron sequence, indicating a mechanistic effect of splicing. To further characterize the myosin gene promoters and to examine the types of enhancer sequences in the genome, we have initiated a screen of C. elegans genomic DNA for fragments capable of enhancing the myo-2 promoter. The properties of enhancers recovered from this screen suggest that the promoter is limited to muscle cells in its ability to respond to enhancers.
Okkema
P G
PG
Carnegie Institution of Washington, Department of Embryology, Baltimore, Maryland 21210.
Harrison
S W
SW
Plunger
V
V
Aryana
A
A
Fire
A
A
D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005091:Exons; D015870:Gene Expression; D005786:Gene Expression Regulation; D007438:Introns; D008969:Molecular Sequence Data; D009132:Muscles / Q000378:metabolism; D016296:Mutagenesis; D009218:Myosins / Q000096:biosynthesis / Q000235:genetics*; D009838:Oligodeoxyribonucleotides; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D015183:Restriction Mapping; D017384:Sequence Deletion; D014170:Transformation, Genetic
D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D009218:Myosins