The E2-C vihar is required for the correct spatiotemporal proteolysis of cyclin B and itself undergoes cyclical degradation.
BACKGROUND: Proteolytic degradation of mitotic regulatory proteins first requires these targets to be ubiquitinated. This is regulated at the level of conjugation of ubiquitin to substrates by the anaphase-promoting complex/cyclosome (APC/C) ubiquitin-protein ligase. Substrate specificity and temporal activity of the APC/C has been thought to lie primarily with its two activators, Cdc20/Fizzy and Cdh1/Fizzy-related. RESULTS: Here, we show that reduction in the E2 ubiquitin-conjugating enzyme (UBC) of the E2-C family that is encoded by the Drosophila gene vihar (vih), by either mutation or RNAi, leads to an accumulation of cells in a metaphase-like state. Cyclin B accumulates to high levels in all mitotic vih cells, particularly at the spindle poles. Vihar E2-C is present in the cytoplasm of mitotic cells but also associates with centrosomes, and its own degradation is initiated at the metaphase-anaphase transition. Expression of destruction D box mutants of vihar in the syncytial embryo results in mitotic arrest at late anaphase. In contrast to hypomorphic mutants, Cyclin B is degraded at the spindle poles and accumulates in the equatorial region of the spindle. CONCLUSIONS: In Drosophila, the Vihar E2 UBC contributes to the spatiotemporal control of Cyclin B degradation that first occurs at the spindle poles. APC/C- mediated proteolysis of Vihar E2-C autoinactivates the APC/C at the centrosome before a second wave of proteolysis to degrade Cyclin B on the rest of the spindle and elsewhere in the cell.[1]References
- The E2-C vihar is required for the correct spatiotemporal proteolysis of cyclin B and itself undergoes cyclical degradation. Máthé, E., Kraft, C., Giet, R., Deák, P., Peters, J.M., Glover, D.M. Curr. Biol. (2004) [Pubmed]
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