Monitoring Editor: Thomas Pollard Mutations in unc-96
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
mutant muscle. However there is no difference in the overall level of paramyosin in wild-type, unc-96
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
, or unc-96
(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.