Regulation of the myosin-directed chaperone UNC-45 by a novel E3/E4-multiubiquitylation complex in C. elegans.
The organization of the motor protein myosin into motile cellular structures requires precise temporal and spatial control. Caenorhabditis elegans UNC-45 facilitates this by functioning both as a chaperone and as a Hsp90 cochaperone for myosin during thick filament assembly. Consequently, mutations in C. elegans unc-45 result in paralyzed animals with severe myofibril disorganization in striated body wall muscles. Here, we report a new E3/E4 complex, formed by CHN-1, the C. elegans ortholog of CHIP (carboxyl terminus of Hsc70-interacting protein), and UFD-2, an enzyme known to have ubiquitin conjugating E4 activity in yeast, as necessary and sufficient to multiubiquitylate UNC-45 in vitro. The phenotype of unc-45 temperature-sensitive animals is partially suppressed by chn-1 loss of function, while UNC-45 overexpression in worms deficient for chn-1 results in severely disorganized muscle cells. These results identify CHN-1 and UFD-2 as a functional E3/E4 complex and UNC-45 as its physiologically relevant substrate.
Department of Molecular Neurogenetics, Adolph-Butenandt-Institute, Ludwig Maximilians University, Schillerstrasse 44, 80336 Munich, Germany.
Thorsten
T
Hoppe
Giuseppe
G
Cassata
José M
JM
Barral
Wolfdieter
W
Springer
Alex H
AH
Hutagalung
Henry F
HF
Epstein
Ralf
R
Baumeister
D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009218:Myosins / Q000378:metabolism; D013696:Temperature; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D018832:Molecular Chaperones; C107348:unc-45 protein, C elegans; D044763:Ubiquitin-Conjugating Enzymes; C063110:let-70 protein, C elegans; D044767:Ubiquitin-Protein Ligases; D009218:Myosins