MEL-26 INTERACTION PROJECT

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The C. elegans MEL-26 Interaction Map

Full-length C. elegans MEL-26 (GenBank accession no. gi:212645231 ) was used as a bait to screen separately two highly complex random-primed C. elegans cDNA libraries by yeast two-hybrid. The first library was constructed by combining equimolar amounts of mRNA from four different N2 samples: (1) males and hermaphrodites (all stages including embryos), (2) starved mixed stage culture, (3) heat-shocked mixed stage culture, and (4) dauer stage. The second library was prepared from mixed stage embryos isolated by bleaching. A detailed description of the libraries and the yeast two-hybrid methods are available in the accompanying paper (Gomes et al., 2013). 40 different MEL-26 partners were identified in the screens, 11 of them with both libraries. A confidence score was computed for each interaction, with18 interactions falling in the high confidence category. 11 previously reported physical interactions were recapitulated. The entire dataset can be downloaded as a excel file from Gomes et al., 2013. It has been submitted to the IMEx (http://www.imexconsortium.org/) consortium through IntAct (PMID: 22121220) and assigned the identifier IM-20907.

The functional significance of the novel interaction between MEL-26 and PPFR-1 was further investigated in Gomes et al., 2013: Katanin is an evolutionarily conserved microtubule (MT)-severing complex implicated in multiple aspects of MT dynamics. In Caenorhabditis elegans, the katanin homologue MEI-1 is required for meiosis, but must be inactivated before mitosis. Here we show that PPFR-1, a regulatory subunit of a trimeric protein phosphatase 4 complex, enhanced katanin MT-severing activity during C. elegans meiosis. Loss of ppfr-1, similarly to the inactivation of MT severing, caused a specific defect in meiosis II spindle disassembly. We show that a fraction of PPFR-1 was degraded after meiosis, contributing to katanin inactivation. PPFR-1 interacted with MEL-26, the substrate recognition subunit of the CUL-3 RING E3 ligase (CRL3 MEL-26), which also targeted MEI-1 for post-meiotic degradation. Reversible protein phosphorylation of MEI-1 may ensure temporal activation of the katanin complex during meiosis, whereas CRL3 MEL-26 -mediated degradation of both MEI-1 and its activator PPFR-1 ensure efficient katanin inactivation in the transition to mitosis.

Reference:
Gomes J-E, Tavernier N, Richaudeau B, Formstecher E, Boulin T, Mains PE, Dumont J and Pintard L. Microtubule severing by the katanin complex is activated by PPFR-1.dependent MEI-1 dephosphorylation (2013), J Cell Biol, 202 (3):431.

 
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