Levels of the ubiquitin ligase substrate adaptor MEL-26 are inversely correlated with MEI-1/katanin microtubule-severing activity during both meiosis and mitosis

Dev Biol. 2009 Jun 15;330(2):349-57. doi: 10.1016/j.ydbio.2009.04.004. Epub 2009 Apr 8.

Abstract

The MEI-1/MEI-2 microtubule-severing complex, katanin, is required for oocyte meiotic spindle formation and function in C. elegans, but the microtubule-severing activity must be quickly downregulated so that it does not interfere with formation of the first mitotic spindle. Post-meiotic MEI-1 inactivation is accomplished by two parallel protein degradation pathways, one of which requires MEL-26, the substrate-specific adaptor that recruits MEI-1 to a CUL-3 based ubiquitin ligase. Here we address the question of how MEL-26 mediated MEI-1 degradation is triggered only after the completion of MEI-1's meiotic function. We find that MEL-26 is present only at low levels until the completion of meiosis, after which protein levels increase substantially, likely increasing the post-meiotic degradation of MEI-1. During meiosis, MEL-26 levels are kept low by the action of another type of ubiquitin ligase, which contains CUL-2. However, we find that the low levels of meiotic MEL-26 have a subtle function, acting to moderate MEI-1 activity during meiosis. We also show that MEI-1 is the only essential target for MEL-26, and possibly for the E3 ubiquitin ligase CUL-3, but the upstream ubiquitin ligase activating enzyme RFL-1 has additional essential targets.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Adenosine Triphosphatases / metabolism*
  • Animals
  • Caenorhabditis elegans / cytology
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / metabolism*
  • Cullin Proteins / metabolism*
  • Katanin
  • Meiosis*
  • Microtubules*
  • Mitosis*

Substances

  • Adaptor Proteins, Signal Transducing
  • Caenorhabditis elegans Proteins
  • Cullin Proteins
  • Mel-26 protein, C elegans
  • cul-2 proteins, C elegans
  • Adenosine Triphosphatases
  • MEI-1 protein, C elegans
  • Katanin