Sequence Requirements for Myosin Gene Expression and Regulation in Caenorhabditis elegans

• Published in: Genetics (Austin) 1993-10, Vol.135 (2), p.385-404
• Main Authors: Okkema, P. G, Harrison, S. W, Plunger, V, Aryana, A, Fire, A
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; Biological and medical sciences; caenorhabditis elegans; Caenorhabditis elegans - genetics; Caenorhabditis elegans - metabolism; Enhancer Elements, Genetic; Exons; Fundamental and applied biological sciences. Psychology; Gene Expression; Gene Expression Regulation; Genetics; Introns; Investigations; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Muscles - metabolism; Muscular system; Mutagenesis; Myosins - biosynthesis; Myosins - genetics; Oligodeoxyribonucleotides; Organ Specificity; Polymerase Chain Reaction; Promoter Regions, Genetic; Proteins; Restriction Mapping; RNA, Messenger - biosynthesis; Sequence Deletion; Transcription. Transcription factor. Splicing. Rna processing; Transformation, Genetic; Worms
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/135.2.385

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.