title: The Caenorhabditis elegans gene unc-89, required fpr muscle M-line assembly, encodes a giant modular protein composed of Ig and signal transduction domains.
abstract: Mutations in the Caenorhabditis elegans gene unc-89 result in nematodes having disorganized muscle structure in which thick filaments are not organized into A-bands, and there are no M-lines. Beginning with a partial cDNA from the C. elegans sequencing project, we have cloned and sequenced the unc-89 gene. An unc-89 allele, st515, was found to contain an 84-bp deletion and a 10-bp duplication, resulting in an in-frame stop codon within predicted unc-89 coding sequence. Analysis of the complete coding sequence for unc-89 predicts a novel 6,632 amino acid polypeptide consisting of sequence motifs which have been implicated in protein-protein interactions. UNC-89 begins with 67 residues of unique sequences, SH3, dbl/CDC24, and PH domains, 7 immunoglobulins (Ig) domains, a putative KSP-containing multiphosphorylation domain, and ends with 46 Ig domains. A polyclonal antiserum raised to a portion of unc-89 encoded sequence reacts to a twitchin-sized polypeptide from wild type, but truncated polypeptides from st515 and from the amber allele e2338. By immunofluorescent microscopy, this antiserum localizes to the middle of A-bands, consistent with UNC-89 being a structural component of the M-line. Previous studies indicate that myofilament lattice assembly begins with positional cues laid down in the basement membrane and muscle cell membrane. We propose that the intracellular protein UNC-89 responds to these signals, localizes, and then participates in assembling an M-line.
authors.affiliation: Department of Pathology, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Benian
authors.forename: T L
authors.initials: TL
authors.lastname: Tinley
authors.forename: X
authors.initials: X
authors.lastname: Tang
authors.forename: M
authors.initials: M
authors.lastname: Borodovsky
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D001483:Base Sequence; D015153:Blotting, Western; D017173:Caenorhabditis elegans / Q000033:anatomy & histology / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D002451:Cell Compartmentation; D003001:Cloning, Molecular; D019084:Fluorescent Antibody Technique, Indirect; D017238:Genes, Helminth; D015801:Helminth Proteins / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D007136:Immunoglobulins / Q000235:genetics; D008969:Molecular Sequence Data; D024510:Muscle Development; D009124:Muscle Proteins / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D009132:Muscles / Q000648:ultrastructure; D009154:Mutation; D009693:Nucleic Acid Hybridization; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics
chemical_list: D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; D007136:Immunoglobulins; D009124:Muscle Proteins; D012333:RNA, Messenger; C098932:Unc-89 protein, C elegans