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Gene Review

unc-54  -  Protein UNC-54

Caenorhabditis elegans

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Disease relevance of unc-54

  • Unlike deletions that occur in Escherichia coli, spontaneous unc-54 deletions did not contain statistically significant direct or inverted repeats at or near their termini [1].

High impact information on unc-54

  • Placement of the three suppressor mutations s74, s77 and s95 on the genetic fine structure map of unc-54 demonstrates that they are clustered near the right end of the map [2].
  • The amino acid sequence of the rod portion of nematode myosin, deduced for the sequence of the unc-54 heavy chain gene of Caenorhabditis elegans, is highly repetitive and has the characteristics of an alpha-helical coiled coil [3].
  • Nonsense alleles of unc-54 express mRNAs that are unstable in smg(+) genetic backgrounds but have normal or near normal stability in smg(-) backgrounds. smg mutations also stabilize mRNA of unc-54(r293), a small deletion that removes the unc-54 polyadenylation site and expresses an aberrant mRNA [4].
  • Because of disrupted MHC A assembly, dominant unc-54 mutants also exhibit a recessive-lethal phenotype [5].
  • We have investigated Caenorhabditis elegans mutants in which altered unc-54 myosin heavy-chain protein interferes with assembly of thick myofilaments [5].

Biological context of unc-54


Anatomical context of unc-54

  • The mutant MHC B also interferes with assembly of wild-type myosin heavy-chain A (MHC A), the product of another MHC gene expressed in body-wall muscle cells [5].
  • In the wild type, a constant ratio of the synthesis of the unc-54-coded myosin B to myosin A, about 2:1, is maintained during the larval stages in which the synthesis of both myosins increases exponentially and rapid sarcomere growth and addition ensues [8].
  • The genetic properties of Tc1 excision, combined with the DNA sequences of the resulting unc-54 alleles, demonstrated that excision was dependent on Tc1 transposition functions in both germ line and somatic cells [9].
  • The deduced myosin II globular head amino acid sequence shows a high degree of similarity with the globular head sequences of the rat embryonic skeletal muscle and nematode unc 54 muscle myosins [10].

Associations of unc-54 with chemical compounds


Regulatory relationships of unc-54

  • In mutants that do not express MHC B or that express defective paramyosin, muscle structure is disrupted and movement is impaired [12].

Other interactions of unc-54

  • Comparison of the unc-54 protein sequence with the sequence of a second myosin heavy chain from nematode, indicates that the globular head sequence S-1 is more highly conserved than the alpha-helical coiled-coil rod [6].
  • These animals have phenotypes consistent with reduction and/or elimination of function of the gene to which antisense RNA has been produced: twitching and disorganization of muscle filaments for the unc-22 antisense constructs and lack of muscle tone, slow movement, and egg laying defects for the unc-54 antisense constructs [13].
  • The effects of mutation in the unc-52 locus are trans acting upon the synthesis of unc-54-coded myosin in a specific set of muscle cells during a defined period of larval development [8].
  • In addition to mutations in sup-20, other mutations causing muscle defects, such as unc-54 and unc-22 mutations, suppress the hypercontracted phenotype of unc-105 [14].
  • The six proteins also cosedimented with thick filaments purified by gradient centrifugation from CB190 mutants lacking myosin heavy chain B and from CB1214 mutants lacking paramyosin [15].

Analytical, diagnostic and therapeutic context of unc-54


  1. Structures of spontaneous deletions in Caenorhabditis elegans. Pulak, R.A., Anderson, P. Mol. Cell. Biol. (1988) [Pubmed]
  2. Mutations in the unc-54 myosin heavy chain gene of Caenorhabditis elegans that alter contractility but not muscle structure. Moerman, D.G., Plurad, S., Waterston, R.H., Baillie, D.L. Cell (1982) [Pubmed]
  3. Periodic charge distributions in the myosin rod amino acid sequence match cross-bridge spacings in muscle. McLachlan, A.D., Karn, J. Nature (1982) [Pubmed]
  4. mRNA surveillance by the Caenorhabditis elegans smg genes. Pulak, R., Anderson, P. Genes Dev. (1993) [Pubmed]
  5. Myosin heavy-chain mutations that disrupt Caenorhabditis elegans thick filament assembly. Bejsovec, A., Anderson, P. Genes Dev. (1988) [Pubmed]
  6. Protein structural domains in the Caenorhabditis elegans unc-54 myosin heavy chain gene are not separated by introns. Karn, J., Brenner, S., Barnett, L. Proc. Natl. Acad. Sci. U.S.A. (1983) [Pubmed]
  7. A selection for myosin heavy chain mutants in the nematode Caenorhabditis elegans. Anderson, P., Brenner, S. Proc. Natl. Acad. Sci. U.S.A. (1984) [Pubmed]
  8. Mutants altering coordinate synthesis of specific myosins during nematode muscle development. Zengel, J.M., Epstein, H.F. Proc. Natl. Acad. Sci. U.S.A. (1980) [Pubmed]
  9. Insertion and excision of Caenorhabditis elegans transposable element Tc1. Eide, D., Anderson, P. Mol. Cell. Biol. (1988) [Pubmed]
  10. Complete nucleotide sequence and deduced polypeptide sequence of a nonmuscle myosin heavy chain gene from Acanthamoeba: evidence of a hinge in the rodlike tail. Hammer, J.A., Bowers, B., Paterson, B.M., Korn, E.D. J. Cell Biol. (1987) [Pubmed]
  11. Splicing removes the Caenorhabditis elegans transposon Tc1 from most mutant pre-mRNAs. Rushforth, A.M., Anderson, P. Mol. Cell. Biol. (1996) [Pubmed]
  12. Myosin heavy chain gene amplification as a suppressor mutation in Caenorhabditis elegans. Maruyama, I.N., Miller, D.M., Brenner, S. Mol. Gen. Genet. (1989) [Pubmed]
  13. Production of antisense RNA leads to effective and specific inhibition of gene expression in C. elegans muscle. Fire, A., Albertson, D., Harrison, S.W., Moerman, D.G. Development (1991) [Pubmed]
  14. C. elegans unc-105 mutations affect muscle and are suppressed by other mutations that affect muscle. Park, E.C., Horvitz, H.R. Genetics (1986) [Pubmed]
  15. Purified thick filaments from the nematode Caenorhabditis elegans: evidence for multiple proteins associated with core structures. Epstein, H.F., Berliner, G.C., Casey, D.L., Ortiz, I. J. Cell Biol. (1988) [Pubmed]
  16. Sequence analysis of mutations that affect the synthesis, assembly and enzymatic activity of the unc-54 myosin heavy chain of Caenorhabditis elegans. Dibb, N.J., Brown, D.M., Karn, J., Moerman, D.G., Bolten, S.L., Waterston, R.H. J. Mol. Biol. (1985) [Pubmed]
  17. Molecular analysis of the unc-54 myosin heavy-chain gene of Caenorhabditis elegans. MacLeod, A.R., Karn, J., Brenner, S. Nature (1981) [Pubmed]
  18. Combinatorial structure of a body muscle-specific transcriptional enhancer in Caenorhabditis elegans. Jantsch-Plunger, V., Fire, A. J. Biol. Chem. (1994) [Pubmed]
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