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.
Máthé
Endre
E
Cancer Research UK Cell Cycle Genetics Group, Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK.
Kraft
Claudine
C
Giet
Régis
R
Deák
Péter
P
Peters
Jan-Michael
JM
Glover
David M
DM
D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002478:Cells, Cultured; D018385:Centrosome / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism*; D017931:DNA Primers; D004330:Drosophila / Q000196:embryology* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D008938:Mitosis / Q000502:physiology*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010447:Peptide Hydrolases / Q000378:metabolism; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D034622:RNA Interference; D017422:Sequence Analysis, DNA; D008941:Spindle Apparatus / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*
C503698:CycB protein, Drosophila; D019926:Cyclin B; D017931:DNA Primers; D029721:Drosophila Proteins; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; C495573:vih protein, Drosophila; D064173:Anaphase-Promoting Complex-Cyclosome; D010447:Peptide Hydrolases