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Author Notes:

Address correspondence to Shoichiro Ono, Department of Pathology, Woodruff Memorial Building, Room 7125, Emory University, Atlanta, GA 30322. Tel.:(404) 727-5945. Fax: (404) 727-8540. E-mail: ono@bimcore. emory.edu

For acknowledgements, see the full article.

Subjects:

Research Funding:

This work was supported by a grant from the National Science Foundation (MCB-9728762) to S. Ono and G.M. Benian, a grant from the National Sciences and Engineering Research Council to D.L. Baillie, and a postdoctoral fellowship from the Uehara Memorial Foundation to S. Ono.

Keywords:

  • Science & Technology
  • Life Sciences & Biomedicine
  • Cell Biology
  • myofibrils
  • thin filaments
  • ADF cofilin
  • actin polymerization
  • unc-60
  • CHICKEN SKELETAL-MUSCLE
  • DEPOLYMERIZING FACTOR COFILIN
  • F-ACTIN
  • FILAMENT TURNOVER
  • YEAST COFILIN
  • CYTOPLASMIC LOCALIZATION
  • BINDING PROTEINS
  • THICK FILAMENTS
  • PORCINE BRAIN
  • ELEGANS

UNC-60B, an ADF cofilin family protein, is required for proper assembly of actin into myofibrils in Caenorhabditis elgans body wall muscle

Tools:

Journal Title:

Journal of Cell Biology

Volume:

Volume 145, Number 3

Publisher:

, Pages 491-502

Type of Work:

Article | Final Publisher PDF

Abstract:

The Caenorhabditis elegans unc-60 gene encodes two functionally distinct isoforms of ADF/cofilin that are implicated in myofibril assembly. Here, we show that one of the gene products, UNC-60B, is specifically required for proper assembly of actin into myofibrils. We found that all homozygous viable unc-60 mutations resided in the unc-60B coding region, indicating that UNC- 60B is responsible for the Unc-60 phenotype. Wild-type UNC-60B had F-actin binding, partial actin depolymerizing, and weak F-actin severing activities in vitro. However, mutations in UNC-60B caused various alterations in these activities. Three missense mutations resulted in weaker F-actin binding and actin depolymerizing activities and complete loss of severing activity. The r398 mutation truncated three residues from the COOH terminus and resulted in the loss of severing activity and greater actin depolymerizing activity. The s1307 mutation in a putative actin-binding helix caused greater activity in actin-depolymerizing and severing. Using a specific antibody for UNC-60B, we found varying protein levels of UNC-60B in mutant animals, and that UNC-60B was expressed in embryonic muscles. Regardless of these various molecular phenotypes, actin was not properly assembled into embryonic myofibrils in all unc-60 mutants to similar extents. We conclude that precise control of actin filament dynamics by UNC-60B is required for proper integration of actin into myofibrils.

Copyright information:

 The Rockefeller University Press.

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