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Vol. 19, Issue 4, 1529-1539, April 2008
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*Department of Pathology,
Graduate Division of Biological and Biomedical Sciences, and
BIMCORE (Molecular Graphics), Emory University, Atlanta, GA 30322
Submitted July 29, 2007;
Revised January 14, 2008;
Accepted January 30, 2008
Monitoring Editor: Thomas Pollard
Mutations in unc-96 or -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 -98 mutant muscle. However there is no difference in the overall level of paramyosin in wild-type, unc-96, and -98 animals. Anti-UNC-98 and anti-paramyosin colocalize in the paramyosin accumulations of missense alleles of unc-15 (encodes paramyosin). Anti-UNC-96 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 paramyosin missense mutants, UNC-98 is increased. unc-98 and -15 or unc-96 and -15 interact genetically either as double heterozygotes or as double homozygotes. By yeast two-hybrid assay 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 -96 may act as chaperones to promote the incorporation of paramyosin into thick filaments.
Address correspondence to: Guy M. Benian (pathgb{at}emory.edu).
Abbreviations used: MHC, myosin heavy chain; MBP, maltose-binding protein; GFP, green fluorescent protein; ELISA, enzyme-linked immunosorbent assay.
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