Sequence requirements for myosin gene expression and regulation in Caenorhabditis elegans

Genetics. 1993 Oct;135(2):385-404.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans / metabolism*
  • Enhancer Elements, Genetic*
  • Exons
  • Gene Expression Regulation*
  • Gene Expression*
  • Introns
  • Molecular Sequence Data
  • Muscles / metabolism
  • Mutagenesis
  • Myosins / biosynthesis
  • Myosins / genetics*
  • Oligodeoxyribonucleotides
  • Organ Specificity
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic*
  • RNA, Messenger / biosynthesis
  • Restriction Mapping
  • Sequence Deletion
  • Transformation, Genetic

Substances

  • Oligodeoxyribonucleotides
  • RNA, Messenger
  • Myosins