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A more recent version of this article appeared on April 1, 2008
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Submitted on July 29, 2007
Revised on January 14, 2008
Accepted on January 30, 2008
*Department of Pathology, Emory University, Atlanta, GA 30322;
Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30322;
BIMCORE (Molecular Graphics), Emory University, Atlanta, GA 30322
Monitoring Editor: Thomas Pollard
Mutations in unc-96 or unc-98 cause reduced motility and a characteristic defect in muscle structure: by polarized light microscopy birefringent needles are found at the ends of muscle cells. Anti-paramyosin stains the needles in unc-96 and unc-98 mutant muscle. However there is no difference in the overall level of paramyosin in wild-type, unc-96 and unc-98 animals. Anti-UNC-98 and anti-paramyosin colocalize in the paramyosin accumulations of missense alleles of unc-15 (encodes paramyosin). Anti-UNC-96 (Mercer et al., 2006) and anti-UNC-98 have diffuse localization within muscles of unc-15 null mutants. By immunoblot, in the absence of paramyosin, UNC-98 is diminished, whereas in paramysoin missense mutants, UNC-98 is increased. unc-98 and unc-15, or unc-96 and unc-15 (Mercer et al., 2006) interact genetically either as double heterozygotes or as double homozygotes. By yeast 2-hybrid and ELISAs using purified proteins, UNC-98 interacts with paramyosin residues 31–693, whereas UNC-96 interacts with a separate region of paramyosin, residues 699–798. The importance of surface charge of this 99 residue region for UNC-96 binding was shown. Paramyosin lacking the C terminal UNC-96 binding region fails to localize throughout A-bands. We propose a model in which UNC-98 and UNC-96 may act as chaperones to promote the incorporation of paramyosin into thick filaments.